Example: "On a Unix system, system files can only be accessed by the root user."
Root, or the "root node," refers to the top level of a file system. Since file systems are organized by directories, the root node is also called the root directory. You can imagine the root directory as the top of an upside down tree, with folders and files spanning beneath it.
Root is also the name of the "root user," which is user account that has administrative privileges on a computer system. Unlike other users, the root user can access any file or folder on a the main hard disk. For this reason, the root user of a Unix system is often responsible for performing system updates and account modifications.