*Man ls*

     The next three fields are three characters each: owner permissions, group permissions, and other per-
     missions.  Each field has three character positions:

           1.   If r, the file is readable; if -, it is not readable.

           2.   If w, the file is writable; if -, it is not writable.

           3.   The first of the following that applies:

                      S     If in the owner permissions, the file is not executable and set-user-ID mode is
                            set.  If in the group permissions, the file is not executable and set-group-ID
                            mode is set.

                      s     If in the owner permissions, the file is executable and set-user-ID mode is set.
                            If in the group permissions, the file is executable and setgroup-ID mode is set.

                      x     The file is executable or the directory is searchable.

                      -     The file is neither readable, writable, executable, nor set-user-ID nor set-
                            group-ID mode, nor sticky.  (See below.)

                These next two apply only to the third character in the last group (other permissions).

                      T     The sticky bit is set (mode 1000), but not execute or search permission.  (See
                            chmod(1) or sticky(8).)

                      t     The sticky bit is set (mode 1000), and is searchable or executable.  (See
                            chmod(1) or sticky(8).)