First: This is a rights and roles system.
With a right you define which actions a user is allowed to perform. If you combine several rights, you get a role!
This is how groups work. Therefore they can be useful to you.
Groups are a practical intermediate level in this context. Because nobody wants to define which rights they should have for each user individually. Groups make it easy for you: You can use them to assign one or more roles to a larger number of users. Your advantage: You can easily manage the permissions and visibility for a larger number of users.
Within the user interface, the concept of groups also makes it easier to invite your users to pages and workspaces.
Instead of inviting each sales representative individually, you can invite the "Sales" group as a whole to a workspace.
In COYO you have the possibility to give only a certain group of users the right to access groups. The right "Invite groups to a workspace / a page / an event" could for example be reserved for team leads to guarantee a better user management.
There is an additional advantage if you have connected an Active Directory. With the appropriate configuration you can see the different groups directly in COYO and develop dedicated roles for them that correspond to the desired tasks and functions within COYO.