Adding users in Linux

Add a user to Linux
Delete a user in Linux
Add a new group to Linux
Add a user to a group in Linux
Change a password
Modify a user in a Linux group
Copy

etc - directory
/etc directory, the passwd and the group files hold all of the users and group information.
These files are essential when logging on to the system.
The newly created user is added to the passwd file -> etc - directory

https://www.developer.com/open-source/manage-linux-users-terminal/