Kit is a female cat that leads new witches into their powers.
It is also revealed that Kit was a witches Familiar. In the episode where Leo and Piper see a marriage counsler, Phoebe casts a spell causing Phoebe and Paige trapped with a demon trying to kill Kit. Phoebe and Paige save Kit who turns into human form. Kit tells them that she will come back to teach Wyatt when he is ready.