Macbook video chat w/o buying extra?

since i plan on buying the macbook does it come with a video chat feature(if i wanted to chat w/ another macbook user) or do i need to buy somethin extra like leopard? i dont have much of a clue on apple b/c i've always had a pc. does just having an aim screenname and the camera in the macbook allow the video chat to work free? it would kinda suck to pay more or extra just for one feature.. muchas gracias