Groups are showing up in the console containing computer records with very little data. They consume licenses but are unmanageable. They are not able to be deleted.
There is the option on a group (right mouse context menu: Import Organizational Unit and Container). This leads to the active directory. Clients and groups are related to the OUs that were imported. The structure and the clients get added in this way.
While the computers cannot be deleted, the containers (groups) can. Right-click on the group and choose delete to remove them.