From Tar Valon Library
A Wisdom is the head of the Women's Circle in her village. She is chosen by the other women in the circle. She is chosen for her skills in healing and foretelling the weather. Wisdoms are often unknowingly able to channel and in the Two Rivers, it was not uncommon for apprentice Wisdoms to die of the sickness that comes when a woman tries to teach herself (TEotW, Ch. 21).
This is a position of great authority. She will decide things like when to plant crops and when to harvest. The Wisdom is generally the equal to the mayor but in some cases can be his superior. Traditionally, the wisdom is almost always at odds with the mayor. Many villages will choose wisdoms from outside the village so that she will not have favourites (TEotW, Ch. 3).
When the Women's Circle holds a trial, the Wisdom pronounces the judgement (TGH, Ch. 46).
A wisdom is chosen for life and very rarely leaves before her death. Depending on the area the wisdom can also be called a Guide, Healer, Wise Woman, Reader or a Seeker, though these may often just be Healers, rather than holding official power.