Revision is "re-seeing" your draft. It occurs during the entire writing process. Reading to revise improves the meaning and organization of the subsequent drafts of your writing. These revisions to your original draft add the "polish" to a final draft that will better meet the needs of your audience and earn a higher grade. When you revise, you read your writing with a critical eye to evaluate the coherence and organization of the writing for your audience.
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Revision Definition/Tips
Creating a "reverse outline" Exercise
Editing is re-reading in order to reword or find better words to strengthen sentences. Sometimes clarification needs to be added and other times sentences can be shortened to better the clarity. Also, unnecessary repetition may be identified and dealt with.
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Proofreading is reading your draft to correct errors in grammar, punctuation or mechanics. These errors are sometimes defined as "surface" errors. Do not rely on your computer's spell check and grammar check. These checks may be helpful for some obvious errors, but these checks are not complete. For example, spell checks cannot distinguish between spelling or usage errors, e.g. there/their/they're, your/you're, to/two/too.
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You may very well be tired of the writing assignment at this point, but careful proofreading and editing eliminates those errors that result in a lower grade, errors that cause you to kick yourself when your assignment is returned. Take a break before you edit and proofread, but don't wait until the last moment.
During the assessment of your writing, your instructor may use editing symbols to communicate with you about your writing.
Link for list of Symbols