Refers to either Contact Groups (Address Books) or User Groups.
User groups are certain groups of users who have the same or similar responsibilities within the organization. Each User Group has its own set of access rights assigned to it. Groups can also have different Object Views.
The Rights to all features that can be accessed in the end user interface. These primarily include the rights to all System Object and Custom Object records, and certain Tools, such as Scheduler, Batch Task and Expense Entry. Rights are assigned by user group.