The purpose of Appointment Confirmation communications (texts, emails, and/or automated voice calls) is to remind people about any upcoming appointments they may have.
Appointment confirmations are configured in Settings > Appointment Confirmations.
The purpose of the Recalls (texts, emails, and/or direct mail) is to notify patients who are coming close to or are past their recall date to schedule their hygiene appointment. Recalls will be sent out only if a patient does not have another appointment scheduled. Recalls can be found in Campaigns > Automatic Communications.