When Manually Scheduling an appointment you can save the appointment with 4 different options.
Save as Draft - appointment is incomplete and has not been sent to the client
Save as Scheduled - admin has finalized appointment and the system will automatically send to the client asking if the appointment will work.
At this stage the booking is still incomplete (as it needs confirmed by the agent)
Save as Confirmed (will confirm and email to client)- booking is completed, the client receives an email
Save as Confirmed (but do not notify client)- booking is completed, the client DOES NOT receive an email