Symbolic Mode
When describing which permissions to change in symbolic mode the first character(s) indicate(s) whose permissions you will alter: the ones for the user (u), for the group (g), for others (o) and/or for all the three together (a).
Then you need to tell the command what to do: you can grant a permission (+), revoke a permission (-), or set it to a specific value (=).
Lastly, you specify which permission you wish to affect: read (r), write (w), or execute (x).
For example, imagine we have a file called text.txt with the following permissions set:
$ ls -l text.txt
-rw-r--r-- 1 carol carol 765 Dec 20 21:25 tex.txt