chmod : Change mode. It can change user, group and others current permission mode to required permission mode. It can do from two different ways.

I. chmod (required party) + (required permission) file name

chmod (required party) - (required permission) file name

required party, like,

u : user 

g : group
                     
o : others

required permission like,

r : read

w : write

x : executable

morty@c137:~/newdir/subdir$ ls -l
-rw------- 1 morty morty 43 May 27 19:45 everyone-rw
morty@c137:~/newdir/subdir$ chmod go+rw everyone-rw
morty@c137:~/newdir/subdir$ ls -l
-rw-rw-rw- 1 morty morty 43 May 27 19:45 everyone-rw

II. chmod (decimal number of permissions) file name

morty@c137:~/newdir/subdir$ ls -l
-rw------- 1 morty morty 43 May 27 19:45 everyone-rw
morty@c137:~/newdir/subdir$ chmod 666 everyone-rw
morty@c137:~/newdir/subdir$ ls -l
-rw-rw-rw- 1 morty morty 43 May 27 19:45 everyone-rw

chgrp : Change the group.

There is a command id -Gn to know what are the groups that we are in.

morty@c137:~$ id -Gn
morty sudo

chgrp (new group name) file name

morty@c137:~/newdir/subdir$ ls -l
-rw-r----- 1 morty morty 52 May 27 19:53 group-r-only
    morty@c137:~/newdir/subdir$ chgrp sudo group-r-only
    morty@c137:~/newdir/subdir$ ls -l
    -rw-r----- 1 morty sudo  52 May 27 19:53 group-r-only

chown : Change the owner of the file, we have not permission to change the owner. only root have permission to change owner. Now we have to do sudo commands with chown

sudo chown (new owner name) file name

morty@c137:~/newdir/subdir$ ls -l
-rw-rw-rw- 1 morty morty 43 May 27 19:45 everyone-rw
morty@c137:~/newdir/subdir$ sudo chown nobody everyone-rw
[sudo] password for morty:
morty@c137:~/newdir/subdir$ ls -l
    -rw-rw-rw- 1 nobody morty 43 May 27 19:45 everyone-rw