usermod -a -G groupname username
sudo groupadd group_name
#to delete the group
sudo groupdel group_name
cut -d: -f1 /etc/group | sort
$ groupadd developers
$ groupadd operations
groupadd [OPTIONS] GROUPNAME
User: the owner of the file (person who created the file).
Group:the group can contain multiple users. Therefore, all users in that group will have the same permissions. It makes things easier than assign permission for every user you want.
groupadd [OPTIONS] GROUPNAME