Traditional Publishing for books:
1. Get an Agent
2. Agent submits work to major publishing houses.
3. Publishing company may or may not offer you an advance, in exchange for some or all rights to distribute your work.
4. Publisher assigns an editor, to work with your manuscript.
5. Publisher prints, distributes, and maybe markets your work. You may need to also market your work.
6. They assign more or less resources to your project, depending on how your book sells in the early weeks of distribution.
7. If your book does well, they may do additional runs, depending on the contract. If your book does poorly early on, they may opt to not do additional runs, and may own the rights, so that you can't take the project elsewhere for another run. Be mindful about how much of your rights you want to give up, when going through contract negotiation.