They are used to define the order in which resources are displayed on the schedules (at the front desk or on the Internet). Categories are displayed in the order they were created; resources contained within a category are displayed in alphabetical order.
You can assign a category to a resource in the “reservation” section, in the “settings” module, in the “resources” menu when you add or edit a resource.
This notion is used to specify the display order of resources in the “reservation” section, in the “manage reservations” module, in the “schedule” menu as well as the schedule that the members can view online.
For tennis clubs that have many courts, the names that are often used are “Indoor”, “Outdoor”, or the name of surfaces such as “Clay”, “Hard”, “Grass”, etc. Clubs having very few courts do not use this notion often.
In squash, this notion is not used very often because all courts are the same and sorting between 2 and 8 courts in alphabetical order is clear enough.
For fitness centers, the people who manage the trainers' schedules do not use this notion. In centers where they manage the schedules of their devices (bikes, treadmills, etc.), they use the type of devices as categories: bikes, treadmills, indoor rower, powerplate, etc.