Approval Groups are groups of people who approve or decline rooms and resources for events. Approval Groups need to have at least one person in them, and they can be attached to any number of rooms or resources.
Only one person from an Approval Group is required to approve a room or resource request.
Check out this clip from Planning Center University.
Click New Approval Group, and then type the name of the group.
Select the box next to Approvers to choose from the list of people in Calendar.
A person must have Permissions in Calendar in Calendar to be added as an Approver.