As the other chap said, there is a difference between English an American. If you are English, a cinema is where you would go to see a film. But if you wanted to see a play, that is real people on a stage, then you would go to the theatre.

Theater is American spelling, Theatre is the British spelling (according to my British co-worker). In the USA a Cinema is only for movies, while a Theater can be for both plays and movies. It is common to go to the Cinema or a Movie-Theater to watch a movie, but you go to the Theater to see a play.