Copy Edit vs. Line Edit

Hi folks!

I’m confused about copy editing and line editing. When I hear about them, sometimes they’re treated as synonyms, sometimes as different things. And when treated differently, the definitions are not always consistent.

Are they different or the same? If different, how so?

Which one is done first? Or are they typically done at the same time as part of the same service?

Does every book need both? I’m not against paying to do things right, but I was expecting three rounds of professional edits (content, line/copy, proofread), not four.