Client profiles are added to your account by either (a) they schedule an appointment with you (and thus a client profile is created automatically) or (b) you add them as a client in the backend. Once a client has been added to your account, all of their information (including name, email, address, appointments, and notifications) can be found within their client profile.
One setting you can change inside a client's profile is the client's status. Clients can either be Active (which means they can book an appointment with you through your scheduler) or they can be Blacklisted (which means that all appointments they book through the scheduler are automatically cancelled).
Here is what it looks like for a Blacklisted client booking an appointment:
First, I went to Main →Lookup Client, and clicked into the client profile I wanted to Blacklist. I switched the status from "Active" (which is the default) to "Blacklist" and pressed "Save":
Now I went over to the scheduler to schedule an appointment as this client:
After I press "Save" from enter the client's information, the client is presented with the same confirmation message as normal, but no emails are sent out to the client about the appointment and if you look in the client's profile you'll see it is automatically marked as a cancelled appointment:
You can also see this from List→Cancelled:
Again, the client won't receive any email confirmation or reminder about the appointment. The scheduler's behavior will look the same, but instead of the appointment being added to the client's upcoming appointments list, it will instead be automatically marked as "Cancelled" since it was a blacklisted client trying to book.