Like other multiuser operating systems, such as Windows NT/2000/XP, Linux uses user accounts to identify users and allocate permissions. Every Linux system has a special user known as the root user. The root user is analogous to the Windows user known as Administrator. The root user can perform privileged operations that are forbidden to other users. For instance, only the root user can perform most system administration operations. By default, the username associated with the root user is root.
You should be judicious in your use of the root account. For instance, you should safeguard the associated password so that no one uses it to compromise your system. Also, you should log in as the root user only when performing privileged operations. Following this advice will help you avoid disasters such as accidentally deleting important files that are protected against access by ordinary, non-root users.