Assuming you mean 있어요 and 이에요/예요, the difference is that 있다 (있어요) describes the state of existing, whereas 이다 (예요) describes the state of being a noun/adjective. Compare to the English words "are" or "is" which both come from "to be." Sometimes they mean to be something, other times they means that something exists. You are Megan. (to be + noun) You are here. (to be in a state of existing here)

있어요/ 예요