There are three types of permissions:
r read the file or directory w write to the file or directory x execute the file or search the directory
Each of these permissions can be set for any one of three types of user:
u the user who owns the file (usually you) g members of the group to which the owner belongs o all other users
The access permissions for all three types of user can be given as a string of nine characters:
user group others r w x r w x r w x
These permissions have different meanings for files and directories.