What is the purpose of group administrator and gpasswd vs usermod
 

Hello.
Maybe the questions sound trivial but I can't fully explain to myself following and there is only instruction how to do it but not discussing fuctionality.
1. What is practical fuctionality of group adminstrator? (gpasswd -A)
What is the role of group administrator?

2. What is the difference between gpasswd -a and usermod -g

I'm confused now.

makes the user the administrator of that groups(private group), so they can add and delete other users to the group, that's the role of the group admin.

simply adds a user to the group

makes the group the users primary group