It is the passwd file located in /etcdirectory.
To view the contents of this file, type; cat /etc/passwd
Note:- You will see more user accounts in this file than you know of. That's because the rest are system accounts which are crucial to the proper functioning of your system
With most Unix-derived systems, "root" is the super-user account.
The root account is the administrative account on Linux; this account has control over everything in the system.
Cipher
A "root" user has the power to do anything on a Linux system. A "normal user" will be assigned some of these capabilities based on what group they are in, but is generally prevented from running any commands that may affect the system outside of their home directory. Users can be granted "sudo" rights, which allows them to run the sudo command and temporarily be granted root privileges.
Ntuser.dat file in the user folder
A file named Ntuser.dat in the user's folder.
In linux adduser and useradd commands are used to add user account.
One root account
chown user file dont forget that you should be owner of the file or root to give privilege to other users to a file
To create a new user account under any Linux distribution use command called useradd. The system administrator is responsible for creating account. Login as root user (or use sudo command).
/etc/passwd
The "whoami" command should show you what account you are currently using.