Basically administrator settings contain the groups so those are either application wise or standalone. After creating the groups , you have to give the access rights to that group. 

Let's assume, sales manager is my group and I assigned that group to user. now have to allocate the access rights so the group user can create new products. And for that have to give the create access of product model to that group.

Also, we can use this groups for visibility, like if want the sales order confirm button can only visible if user having manager group.