"At the most basic level, there are three types of access: Read
-- the ability to open a file and read it
Write -- the ability to write the file
Execute -- the ability to execute (run) the file
"Directories, though similar, are subject to special rules.
Write permissions on a directory imply that you can create new
files and directories within. Execute permissions are required to
'cd' into the directory, and read permissions are required to list
the contents ('ls').
"You will generally see permissions represented as r, w, or x;
for read, write, and execute. Running 'ls -al' on the command line
will show three sets of these strung together."