During the Age of Legends Healing was developed to almost perfection; except death they could Heal every physical illnesses. Unfortunately most of the knowledge got lost during the Breaking and in the Aes Sedai of the Third Age were only able to perform a so called battlefield first-aid Healing which was used as a rough-and-ready method during the War or Power. 
After the foundation of the White Tower and the formation of the Ajahs, Healers typically joined to the Yellow Ajah. When a Novice or Accepted showed signs of the Talent of Healing it was expected for her to join the Yellow.
There are though examples of mixtures of Talents, so Aes Sedai of a different Ajah also can show a fair amount of skill and Talent in Healing, despite a choice another Ajah. Moiraine Damodred is a good example of being quite Talented in many forms of the Healing, and she joined the Blue Ajah.
Known types of Healing
There are several types of Healing. They require the use of different Powers woven together. Spirit is the most important part of every Healing weave. The more complex ones use all the five Powers.  Nynaeve uses all five, as does Damer Flinn. The Healing weaves of saidin works differently than weaves of saidar; male and female Healers cannot use Healing the same way. In some special cases, e.g. Healing Severing of a channeler requires the Healer being the opposite gender as the healed one to restore full strength in the Power.
First Aid Healing
Aka "Traditional Healing" during the Third Age. The method heals everything in the body at once, nothing can be left out.
After identifying all injuries with Delving, the female Healer weaves Spirit, Water, and Air, and eliminates all physical ailments at once using the patient's body energy for the Healing. This method was used as a battlefield first-aid during the War of Power because only this method could heal injuries inflicted by a Myrddraal's Thakan'dar-wrought blade. Most probably that's why this is the only method which survived, because that one was learned by and used the most extensively. Although it is considered as 'one' method, depending on the Healer's personal mixture of skill/Talent/Power-level the possibilities of the use vary. Very Talented Healers of the Yellow Ajah such as Suana and Samitsu are able to accomplish this.[verify] Although the major advantages and disadvantages apply.
Small wounds and scars vanishe instantly, visible to all viewer's eyes, while larger wounds will close and heal as if they had healed naturally, but do so in mere seconds.
Lost appendages cannot be replaced and truly grievous wounds will leave a visible scar.
It uses the body energy of the injured person. The more serious the injuries are the more energy the Healing requires. In case of a very serious injury it could kill the patient by draining their energy, so in such cases Aes Sedai were not able to do anything with this method of Healing.
Starving to death as a consequence of the Healing
Once a patient has been Healed in this manner, his energy reserves must be replenished. The patient usually feels imminent increasing hunger. In case of a serious injury or illness the patient will be unable to stand under his own power without eating a huge amount of food and literally would starve to death. One example was Mat Cauthon's Healing in the White Tower, severing his connection to the dagger from Shadar Logoth. For days afterwards Mat was given five times as much food to replenish his strength.
Energy drainage of the Healer
It requires a disproportionate amount of strength from the Healer so in case of many injured, the Healer's strength might not last long enough.
See information about similar kind of Healing performed with saidin here.
Long-term process Healings
This is a category where several different Healing cases fall. Knowing that in the Age of Legends they could heal any physical injuries and illnesses with advanced and very complex Healing methods, most probably all Healing except the first aid Healing fall into this category. In comparison, most probably they could be applied on only a particular part of the body, so in case of a serious injury, the death as a consequence of the Healing did not apply to these methods.
Required less strength from both the Healer and the healed person, though it still required a fair amount.
A month or more time needed for full recovery. It left visible scars although less serious ones compared to natural healing of the body.
Depending on the skill/Talent/Strength in Power of the Healer, this method can be applied from the level of reducing the pain to the level of wiping it out completely. Requires higher level of ability in Healing. In correlation with the skill/Talent/Strength in Power of the Healer the patient might feel drowsiness, or simply result in unconsciousness.
This weave washes away fatigue from muscles. Although the healed person feels similarly full of energy as after a good sleep, physically the body is not refreshed completely, the energy deficit has its consequences, so the normal ways of recovery would be needed. It cannot be applied constantly. In this method skills and Talent are more important factors than strengths in Power. Moiraine was particularly good at this kind of Healing.
There is a male version of this weave, used by Antail on Inturalde. "Another wave of Power washed through Ituralde. it was like a broom sweeping through him, pushing away all of the fatigue and confusion, restoring his senses and making him feel as if he'd a perfect night's rest. His right eye didn't hurt anymore. There was something lingering, deep down, an exhaustion in is bones. He could ignore that."  Antail tells him that this Weave is more dangerous than the women's version, as he was told. Although in some way, it is more effective.
Relations with the One Power
More factors affect the success level of Healing. The strength level in the Power and the amount of Talent possessed, and the skill of the Healer, he latter two more so than strength in the Power. With less Power but more skill and Talent one can perform better Healing. Some of strongest Aes Sedai were only able to Heal bruises while other weaker ones were excellent Healers.[verify]
Healing with the True Power instead of the One Power, Elan Morin Tedronai cured Lews Therin Telamon of his madness temporarily. He calls it Shai'tan's Healing and despite that he admits that he was never talented in Healing, he is able to give the Dragon his sanity back, so that he can realize what had he done to his loved ones. The method causes Lews Therin extreme distress and suffering.  By the description of the method it is clear that it's very different from the one Nynaeve invents when Heals Naeff from his madness.  While the former happens quite quick and is described as temporary the latter requires time and patience and its effect is permanent. Rand/Lews Therin comments that even the most Talented Healers during the Age of Legends had difficulty with diseases of the mind and many believed that madness could not be Healed with the One Power.
Healing a channeler
Only channelers who were forcefully cut from the True Source can be Healed. Unfortunately those who burned out by accident cannot. Also the Healing is only fully successful if the Healer is of the opposite gender. Otherwise channelers will not gain back their full strength in Power. After Healing Severing the healed channelers gain back their Talents as well.
Healing attempt on Rand's madness
After Nynaeve finds out that she could actually Heal the madness caused by the taint of saidin, she tries to Heal Rand's madness too. When she Delves him she finds the darkness so enormous, covering the entirety of his mind, thousands upon thousands of tiny black thorns pricked into his brain that she understands that she would not be able to remove them. On the other hand she finds something like a brilliant white lacing of something beneath the blackness of the thorns, radiating white like liquid Power. Light given form and life. Coated each of the dark tines, driving into Rand's mind alongside them.
Nynaeve attempts to unravel the web of Graendal's Compulsion from the mind of Kerb and she manages to do so with the use of all five Powers, although it leads to the almost imminent death of the boy with only a few minutes of not even complete sanity before the death. The success of the removal might most probably depend on the level of Compulsion. Unraveling the web of Kerb's Compulsion took almost an hour for Nynaeve and drained her strength rapidly. Although this was her first attempt to apply such Healing method.
Graendal, who is an undisputed master of Compulsion can remove her own Compulsion from Ramshalan leaving him dazed and disoriented but alive.
Semirhage is also able to remove Compulsion. She knows though, that removing even a very weak Compulsion could have a very nasty effect on a person. The brain could be harmed seriously. 
Rand/Lews Therin skills regarding Healing
Before he merges with Lews Therin Rand thinks about learning more on Healing. When he is already having great access to LTT's memories he is able to advise Nynaeve to a certain level how to remove Compulsion, and he is sure that it can be done. "I have little skills with this kind of weaving. I suspect that you can remove Compulsion, if you try. It is similar to Healing, in a way. Use the same weave that creates Compulsion, but reverse it." Rand also knows that the boy's brain will be damaged seriously after the process but that was also the effect of the powerful Compulsion already. LTT had seen that kind of effect dozen of times.
Healing with saidin
Gender based differences
Healing with saidar is accompanied by a great chill rippling through the body; contrarily, Healing with saidin it is accompanied by a great wave of heat.
Traditionally the Aes Sedai use the Delving weave before performing Healing as a way to look for injuries and illnesses in a body.
New-Old Healing method rediscovery
Nynaeve al'Meara is the one who in her desire to make Healing more efficient rediscovers a more complex method of Healing which requires the use of all five Powers. So does Damer Flinn and Sumeko Karistovan of the Kin, independently from Nynaeve. Compared to the only known, "traditional" Aes Sedai method, these new methods are far more effective and they avoid most of the negative side effects of the former one.
People possessing the Talent
- All Yellow Ajah
- Aginor/Osan'gar, posing as Corlan Dashiva he taught some Healing weaves to Damer Flinn and other Asha'man
- Alanna Mosvani, she demonstrated some talent Healing Rand after the Battle of Dumai's Wells
- Anaiya Carel, she demonstrated some talent trying to Heal Verin Mathwin after a unfortunate adventure in Tel'aran'rhiod
- Antail, he is a good Healer among the Asha'man, inventor of a weave that revitalizes exhausted people
- Asra Zigane, despite her weakness she is a very talented Healer
- Cadsuane Melaidhrin, she demonstrated some talent Healing Rand and Nynaeve after the cleansing of saidin. Cadsuane describes her ability in Healing as "no more than average". 
- Chesmal Emry, considered a very good Healer, she used her talent also to kill people without leaving a trace
- Corele Hovian, she is considered among the best Aes Sedai Healers
- Dagdara Finchey, she is among the best Aes Sedai Healers
- Damer Flinn, he is the best Healer among the male channellers, rivalling Nynaeve's talent
- Elaida do Avriny a'Roihan, she demonstrated some talent Healing Moiraine Damodred during her training as Accepted
- Gabrelle Brawley, she demonstrated some talent Healing Logain Ablar during the Last Battle
- Jahar Narishma, he performed some preliminary Healing on Lan after his combat with Demandred
- Joline Maza, she demonstrated some talent in Hinderstap
- Masuri Sokawa, she is quite good in the traditional Aes Sedai method of Healing, she is also good in the weave that removes weariness
- Merilille Ceandevin, she Healed Windfinders in the Kin's Farm
- Moiraine Damodred, her Talent was particularly strong. 
- Myrelle Berengari, she is described with a little talent in Healing, but no more than Siuan Sanche
- Nyneave al' Meara, she is one of the most talented Healers of the current era
- Pevara Tazanovni, she demonstrated some talent many times
- Samitsu Tamagowa, she was considered the best Aes Sedai Healer until the arrival of Nynaeve
- Semirhage, in the Age of Legends she was among the best healers but used hers skills also to inflict pain for her pleasure; she was even able to remove Compulsion from Elza Penfell's mind
- Seonid Traighan, she demonstrated her talent Healing a badly wounded Aiel tortured by Perrin Aybara
- Sharina Melloy, she demonstrated a great talent in the new weaves introduced by Nynaeve
- Siuan Sanche, she demonstrated some talent many times
- Suana Dragand, the Yellow Ajah Head is in the first rank in the Talent of Healing. Her abilities were so great that no sister, not even those much stronger than her, could do better, with the possible exception of Samitsu. But this was before the arrival of Nynaeve
- Sumeko Karistovan, she is the best Healer among the Kinswomen, rivalling Nynaeve
- Teslyn Baradon, she demonstrated her talent Healing a badly wounded Egeanin
- Vandene Namelle, she demonstrated some talent Healing Moiraine in Tifan's Well
- Verin Mathwin, she demonstrated some talent many times
- The Wheel of Time Companion, Yellow Ajah
- The Wheel of Time Companion, Healers
- The Wheel of Time Companion, Healing
- Towers of Midnight, Chapter 28
- The Eye of the World, Prologue
- Towers of Midnight, Chapter 15
- The Shadow Rising, Chapter 3
- The Wheel of Time Companion, Healing
- The Gathering Storm, Chapter 22
- The Gathering Storm, Chapter 33
- Winter's Heart, Chapter 35
- The Dragon Reborn, Chapter 3