Depending on your publisher, there can be quite a few people involved in getting your book to market. Even if you self-publish, there are still many functions that you may not do yourself.
Below is not an exhaustive list, but a rambling stream of consciousness when thinking about the various jobs and the people who are involved in the publishing process:
author (kinda important)
literary agent (we think this is kinda important too)
acquisitions editor
publisher (the boss of the editorial and acquisitions team)
editorial director (the one who hires the in-house editors)
contract department (legal)
substantive editor (aka developmental editor)
line editor
copy editor
proofreader (more than one?)
managing editor (the one who manages the editorial workflow for multiple books simultaneously)
production manager
ISBN agency
typesetter
cover designer
art director
interior layout designer
copywriter (back cover and catalog)
printer (there is another full team involved at the printer’s)
warehouse team
copyright office
chief financial officer
accountant (who pays the bills)
marketing director
publicity personnel
sales manager
salespeople (multiple in every publishing company)
special markets sales person
foreign rights manager
subsidiary rights manager (often the same person as above)
SEO manager (digital strategies)
metadata data entry (double-check all the details)
online store coordinator (each “store” has a different person)
brick & mortar store buyers
online or in-store merchandising manager
ad designer
AND the reader who buys one copy of what everyone above helped create.
Add any that I missed in the comments below.
By the way, none of the above jobs is done for free. Thus, the challenge of the economics of publishing.
If everything works well, the group can create this picture: