Saria is not the actual leader of the Kokiri, a forest tribe that never ages older than children appearance, but she is their mentor. In Ocarina of Time, when Link is brought into shelter of the Great Deku Tree by his fleeing mother, Saria takes over the task to look after the baby.

Later on it is revealed to her and Link that she is actually Sage of the Forest and therefore has to reside within the Chamber of Sages in the Sacred Realm, to help keep protecting Hyrule and the Goddesses' realm at least a little bit from the claws of evil.