What’s the difference? The terms seem to be interchangeable, but of course, they are not. The term editing often refers to the process that can be divided up into three distinct stages.
After finishing a first draft, you begin revising. Revision is the act of moving around sentences and paragraphs to make sure the content, or what you are saying, is in the right place and in the right order. Checking word choices, spelling, and punctuation is a waste of time at this point because many of the actual sentences will be changed, and some sentences and even whole paragraphs may be deleted entirely.
Editing, as a stage rather than the umbrella term, involves looking carefully at your word choices, or diction, as well as sentence structure, or syntax. These are important choices that writers need to make. Do you need a metaphor or simile to make the work more clear and interesting? This is the time to add it.
Proofreading is necessarily the last step in the editing process. In this step, every bit of punctuation must be examined, which means identifying types of sentences and deciding where commas, semicolons, and periods go. At the end of this stage, all typos must be caught, and every word needs to be in its place.
Almost anyone can write; you only have to move your fingers over the keys, but editing reveals who can write well.