(of a person) of what character, origin, position, importance, etc.: Who does she think she is?
the person that or any person that (used relatively to represent a specified or implied antecedent): It was who you thought.
(used relatively in restrictive and nonrestrictive clauses to represent a specified antecedent, the antecedent being a person or sometimes an animal or personified thing): Any kid who wants to can learn to swim.