The volunteer screen can be used to quickly see what volunteers will be available, set schedules, or as a timecard for the volunteers themselves. You're able to use all, some or none of these features at your discretion.

If you're logged in as an admin, you'll see a section on the Volunteer Screen where you can manage volunteer schedules and timecard entries. If the logged in user is ONLY a volunteer (see permissions under users), then they'll only have access to the volunteer screen plus the ability to clock in or out.

Volunteers can be added or removed by admins from the Person screen or from Settings | Users