Definition of Guests group in The Network Encyclopedia.
What is Guests Group?
Guests Group is a Microsoft Windows built-in group existing on all Windows-based servers and workstations (Windows 10). The Guests group is a local group whose initial membership is the built-in Guest user account. If a member server or workstation joins a domain, the global group called Domain Guests is added to the local Guests group.
The Guests group has no preassigned rights or permissions on Windows NT domain controllers and has a single right, Log On Locally, on the Windows NT member server or workstation on which it exists. You can assign any network resource permissions to this group in order to grant temporary or guest users the access they require.

Guests group members rights
Members of the Guests group do not have the right to make permanent changes to their desktop settings. The Guests group is also a built-in local group on machines running Windows 2000 that are not part of a domain.