Editing is often split into different functions, eg: copy editing, line editing etc but what it comes down to is checking inconsistencies and fluency of the manuscript.
Copy Editing includes grammar and consistency issues eg ensuring that people’s names are correct throughout and the spelling doesn’t change; place names are the same etc. A copy editor finds issues of continuity that don’t add up.
Line editing involves moving lines around so they are clearer. Shortening sentences if they go on too long, lengthening them if they are too short and it breaks the story up. Checking the words are appropriate to the manuscript (eg not using long complex words in a children’s novel). They make sure the story flows and doesn’t stop or run out of steam.
For our purposes we put it under one banner and call it Editing.
Editing takes 2 to 5 weeks depending on the complexity and length of the book. It costs £25 an hour and an editor can get through about 10 pages in an hour though this will decrease if there are a lot of corrections to be made.
Proofreading looks at basic grammar and spelling errors. We check for things like their/there/they’re and common mistakes as well as missed words and excess spacing.
It normally takes up to one week for a normal length novel (50,000 words) to be proofread.