On the system, each user that is created exists with its own profile. This includes a password, home folder, mailbox, and corresponding configuration files within that home folder.
This doesn't mean every user can access the server's command line. By default, account users in cPanel cannot, unless specifically given access by the server administrator.
However, in the back-end, changing this access is a simple value change in the file that contains all the users on the system, instructing the system to use a particular "shell" for that user's access. Without a shell, or with a "noshell" shell defined, that user will not be able to access the command line.
A "jailed" shell is often provided, providing a compartmentalized environment that limits access to areas on the system. This helps improve security and simplify server operations.