In linux file permissions are sometimes represented by 3 octal digits, being a combination of read (4), write (2), execute (1).

The first digit represents the file permission for the user who is the owner of the file, 5 being a sum of 4 and 1 meaning the user can read and execute the file.

The second digit represents the file permission for the associated group of the owner of the file, 1 being permission to execute the file.

The third digit representing the file permission for users who are "other", those who are not the user defined as the owner of the group nor part of their group of permissions, 1 being permission to execute the file.