Users in Linux could be managed using command-line tools or via graphical applications. The most common command-line tools in Linux for user creation are adduser and useradd, while most desktop environments and Linux distributions will have a graphical tool which basically is just a frontend to these command-line tools.
All these tools will eventually write related user information in /etc/passwd, /etc/group and /etc/shadow files. They'll also create user home directory and populate the home directory with necessary files stored in /etc/skel.
Graphical methods to create user for different Linux distributions:
adduser is an interactive command-line tool to add new users in Linux. You can run the command at the terminal with just a username as argument and follow along the interactive process to create a user.
$ sudo adduser username
[sudo] password for user:
Current user needs to have administrator privilege on the system.
Adding user `username' ... Adding new group `username' (1001) ... Adding new user `username' (1001) with group `username' ... Creating home directory `/home/username' ... Copying files from `/etc/skel' ...
New password: Retype new password: passwd: password updated successfully
Changing the user information for username Enter the new value, or press ENTER for the default Full Name : Room Number : Work Phone : Home Phone : Other :
Is the information correct? [Y/n] y
Manual: adduser(8) - Linux man page
Comment anonymously. Login not required.