Translation:The movie is enjoyable.
재미있다/재밌다 - interesting, fun to do (or fun to see, watch, read, etc.)
즐겁다 - optimistic, joyful, upbeat, gay (in the original meaning)
It is an irregular verb with its stem ending in ㅂ. Check this out for more info http://www.koreanwikiproject.com/wiki/ㅂ_irregular_verbs
You can see the same change with verbs like 고맙다, 어렵다, and 춥다 :)
Ok I'm a Canadian native English speaker. No one will actually say that the movie is enjoyable; they would probably say fun instead.