|Users, Groups, and Permissions / Working with Groups and Departments|
Groups are associated with a home site, which represents the home site where the users in the group typically work.
For example, cardiologists who work at the Society Hill site could belong to a group called Cardiology whose home site was also Society Hill.
Members of a group do not have to belong to the same site, however. For example, you could create a Cardiology group with members from the Society Hill site, the West Philadelphia site, and the Old City site. In this situation, you typically assign the Cardiology group to the Global site to indicate that its members span multiple sites.
If you are not working in a multi-site deployment, you must associate all your groups with the Global site.