Revising something is also known as drafting. So when you Revise your paper you are editing it. This means things like correcting spelling errors and the sorts.
The word, re- means again. Vision is to look. Therefore, look again. It can include, revising your test (looking it over again), revising your essay (looking and checking it), or you can say a revised edition of the encyclopedia was published - means the book was edited.
