I get asked this a lot and have a hard time explaining verbally, so I thought I’d show you. One of my prospects has kindly granted permission to share a piece I did for him just recently to show how I can change simple words on a page into something better. Sorry, this looks like a long blog, but all you’re doing is reading the same piece of writing, written three ways, so please read on for a simple explanation of the craft of the proofreader/editor/writer, as told through words – note that some information has been changed, and links removed, for confidentiality.
Below is the original piece. I've left some Microsoft Word highlights obvious just for guidance.

I then did a proofreader's job on it. This is a review of all mechanical issues with the writing, like spelling and grammar, and would also correct any obvious factual inaccuracies. It leaves the style of the writing unchanged - it doesn't polish a piece, just corrects the use of language. This service is great for people who are confident in their written skills, but want to make sure a piece is 100% correct before it goes public. Here is the piece after proofreading:

After this it was clear that the piece could benefit from having a copy-editor work their magic on it to tidy up the language and increase the overall readability. A copy-editor uses the base text to work with, but as well as correcting any errors, they also review how the piece fits together. This service is useful for those unsure of how their message is written, or seeking guidance on clarity. Here is the copy-edited version:

You can see that the structure of the piece was changed, to describe the charity first, then explain about how donations to them are so cost-efficient. Then the final 'call to arms' was redrafted to remind people of the link and encourage, rather than hope for donations. With such a substantial revision, this is a 'heavy' copy-edit job, verging on rewriting. What we in the profession call 'light touch' is also available - that would minimise alterations to preserve more of the original style.
That's what I do, when editing and proofreading. I'll generally ask to see work before recommending a service, so that clients get the best service possible. Of course, if all you have are some bullet points and a vague idea, I'll switch into copywriter mode and do the whole thing for you.
Please, get in touch with me on my contact page to see how I can help you tell your story.
