I'm learning Korean grammar and I had the phrase "뭐예요" in this notebook I usually have with me with notes from websites about korean grammar and it was as an example of a question phrase, and I was talking to a korean friend about grammar so he saw that phrase in my notes and said that it should be "뭐에요". I forgot to ask him the specifics of that though and it was on exam return day right before the summer, so I can't really ask him about it. I looked up both of the phrases and it looks like perhaps people use both but I have no idea, and I couldn't find any sites that explain the phrases, so could someone explain to me the specifics of this phrase and/or which one is correct? thanks in advance!! btw just for clarity's sake I'm trying to say "what is this/that/it".