Areas are often used by large instances as a way of organizing/restricting users, customers, inventory pieces, etc.
To assign a tech/rep/user/customer/inventory piece to an area, click to edit the applicable profile/detail page, and find the 'Area' dropdown menu. Select an area from the dropdown:
Click 'Save and Close.'
(You can also assign areas when mass creating users. See help article 'Onboarding Users/Reps from Front End' for more information.)
RESTRICT USERS BY AREA (ADMIN):
Login to the Admin (back end) portal of your FastGem instance, click 'Users,' then click 'Manage':
Click the name of the user you wish to restrict by area: