Appointment schedulers are business tools that allow clients to book models, reschedule appointments, and cancel appointments through a web interface. It also allows clients to see the certain services that any particular model has available on her profile page. When clients want to make an appointment with a model, they go to your business's website, or anywhere else the booking software is supported, and choose an available date and time with the model of their choice.
On the backend, you enter parameters about when clients can book certain services, based on business hours you set, as well as the times and dates that your staff or other resources are available. The app also prevents double-booking and over-booking, and gives you the flexibility to block off times when certain services may be unavailable.
Say you run a model agency business and your top model takes a two-week vacation. You can enter her days off in the appointment scheduling app ahead of time so that your clients won't be able to book any model appointments during the days that she's on vacation.