If you missed today's Editorial Elevenses about the stages of editing, you can go to the Loomis and Lyman Facebook page and watch the replay.
As discussed during Editorial Elevenses, there are four stages of editing: developmental editing, line editing, copy editing, and proofreading. Editors look for different things at each stage, so the stages aren't interchangeable. For example, proofreading and copy editing are not the same thing.
So how does knowing this save you time and money? Most authors today are self publishing or are working with an independent publisher. Most authors are left to find editorial support on their own. Most authors don't have a lot of money to spend. Knowing the difference between each editorial stage can help you spend your money wisely. You'll know what you're asking for.
Knowing what service you need saves time for both you and the editorial professional. If you know your manuscript needs a copy edit instead of a proofread, you can target your "ask" to copy editors. Someone who just does developmental editing won't respond to your ad, saving your time and the editor's.
Knowing the stages of editing saves you time because you won't have to renegotiate the scope of work. If you ask for a proofread when what you really need is a copy edit, the editor will come back to you and say, "This needs to be copy edited. I can do that for you, but it will take this much more time and cost this much more money." There goes your schedule and your budget. Plus, if you dither too much about what your manuscript needs, the editor is likely to tack on a PiTA fee. PiTA stands for Pain in the Ass. Pita is something you eat; don't be a PiTA. Knowing what you need is good for the wallet.
So, in addition to the Editorial Elevenses on the topic, where can you go to find out more about the stages of editing? My favorite resource is Louise Harnby. She has amazing resources for writers and editors, including a fantastic blog post about the levels of editing, which can be found here.
To see what the different levels of editing look like, samples can be found here.
Every editor has their own style. Keep in mind that one editor's developmental edit will differ from another's, copy edits will differ, even proofreads will differ. The key is finding an editor who works well with you. Knowing the stages of editing will make your search for an editor easier and less costly.