Hi,
it is for grouping VM/CT and storage. Then user groups can be allowed access to a resource pool and therefore have access to the resources in it. No need to define access rights per single resource.
As example: I created a group of containers and VM and assigned them to a pool. Then I provided access to a user group to this pool. Voilá, all users in the group had access without the need to set the access rights one by one.
It is nothing fancy, but if you have multiple tenants it makes configuration of access rights easier.