Internally, the system keeps track of files and directories using inodes. An inode (or index node) is a representation of a file that stores all the data belonging to that file, such as owner, type, size, access permissions, access times and the file's layout on disk. Each inode has a unique number which is used by the system in file handling operations: the filename is simply a device to make the filesystem easier to use for humans. In fact, while a file may have only one inode number, it may have several filenames, these being links to the one inode. See ``Creating links to files and directories'' for more information on links to files and directories.