Hobbes is a stuffed tiger.
Calvin is a rambunctious little 6 year old.
When playing by himself, Calvin imagins Hobbes as being alive, to be his playmate. So Hobbes is really just a figment of Calvin's very wild imagination. So, to everyone else hobbes is just a stffed animal tiger that Calvin brings along everywhere. But to Calvin, hobbes is his "very alive" best friend.
Hobbes just stands for childrens imaginations, and if you believe in something enough, it becomes real and alive to you personally.
Anyways, Calvin and Hobbes is my absolute favorite comic strip!! I have like 5 of their books and i never get tired of them!!!
Anyways, sorry bout' rambling on so, hope it helps clear up any confusion about Calivn and Hobbes!!