The job titles vary wildly from country to country and house to house. The most usual ladder I've seen in the UK is
Editorial Assistant: entry level. Quite often drawn from work experience or PAs who want to get into editorial. You do a lot of admin.
Assistant/Junior Editor: Your first promotion. You do a lot of admin and might have a book or two to process on your own - paperbacking, that sort of thing - though a more senior editor is probably has overall responsibility.
Editor/Desk Editor: You have authors of your own and you're responsible for those books, from start to finish. You don't acquire or commission, though - someone more senior buys a book, eases you in, and leaves you to get on with it.
Commissioning Editor: You're now expected to acquire stuff as well.
Senior Editor: You have a lot of books under your belt at this point, and you're very good at what you do. You've probably specialised quite a lot, as well.
Editorial Director: You run at least one list, and Editors of all kinds report to you. This is a job that you can in fact come in straight in to from a senior position somewhere else - maybe you were an agent, for example, or a packager. Your hands-on editing is probably confined to a few high-profile authors.
Publisher: You have overall editorial and business responsibility for an entire imprint. In children's publishing, you might have one Publisher for the picture book list, one for Fiction; that sort of thing. You aren't necessarily an editor by background (but you probably are.)
MD/CEO: You run the company.
You might also have a Managing Editor; that's a term that can mean a few things, but in my experience it's a kind of super-admin person. That's the person you pray doesn't fall under a bus.
