Q. What makes am animal clean, or unclean according to the Torah?

A. A clean animal must have cloven hooves, and chew the cud, e.g. a cow has cloven hooves, and they chew cud. A pig has cloven hooves, but they don't chew the cud. Rabbits chew the cud, but they don't have hooves. You get the idea.

Note: There after rules for seafood as well, but I am unfamiliar with those.