When writers revise a rough draft, they literally "resee" their subject — and then modify the draft to fit the new vision. Revision is more than just tinkering with a word here and there; revision leads to larger changes — new examples or details, a different organization, or a new perspective. You accomplish these changes by adding, deleting, substituting, or reordering words, sentences, and paragraphs.
Although revision begins the moment you get your first idea, most revisions are based on the reactions or anticipated reactions of the audience to your draft. You often play the role of audience yourself by putting the draft aside and rereading it later when you have some distance from your writing. Wherever you feel readers might not get your point, you revise to make it clearer. You may also get feedback from readers in a class workshop, suggesting that you collect more or different information, alter the shape of your draft to improve the flow of ideas, or clarify your terminology.
As a result of your rereading and your readers' suggestions, you may change your thesis or write for an entirely different audience. Revising also includes editing to improve word choice, grammar, usage, or punctuation and proofreading for typos and other surface errors.
