hmmmmmm....

I read to the bottom of the pag I found telling me how to add the user to a
group and found this:

The usermod command has two options for adding users to groups. The "-g"
option changes the user's primary group. The "-G" option adds users to
secondary groups. With the "-G" option, more than one group can be
specified by placing a comma (,) between the group names.
If you do not specify the "-a" (append) option with "-G", the user will be
removed from all secondary groups except the groups listed.

So what does that mean?