What does the `user` do in nginx conf

Question

user git;

I think the user means you run the server with the account.

Can I use multiple users in nginx conf?

If one user has permission issue, then nginx will try another account to access the file?

# user www-data git gitlab poc;
user git;
worker_processes 4;
pid /run/nginx.pid;

Answer 1

I think the user means you run the server with the account.

Correct; the nginx process(es) are run as that user.

Can I use multiple users in nginx conf?

No.

If one user has permission issue, then nginx will try another account to access the file?

No. Ensure the user whom you have set to run the server as has all of the needed permissions.