The various file and directory permissions, typically set using chmod.

FILE
r #read, view,copy
w #write, change (typically requires r permission also)
x #execute - file can be run as a process
s #execute as USER/GROUP owner instead of user running command
S #special bit set but not execute - ERROR
t #sticky bit - can only be deleted by user owner or root

execute is typically OFF by default for new files

DIRECTORY

r #directory content can be listed
w #files can be added or removed (typically requires x permission also)
x #allows user to navigate INTO the directory, and access files/subdirectories
s #new files/directories are created with same group owner as that of the host directory
t #sticky bit - all files/directories created within can only be deleted by user owner or root
T #sticky bit as above but others do not have execute permission