These settings determine which emails will be sent for admin-entered reservations
The first checkbox (set reservation as confirmed) will automatically confirm the reservation and so there will be no need to send the new reservation email -- instead the reservation confirmed email will be sent.
The second checkbox (send emails to client) can be switched off if you don’t want any emails to be sent to the customer at this time. If this option is selected, a single email will be sent (which one is sent depends on the first checkbox). This option has no effect on the emails sent to the administrators. This will happen based on your notification settings (by default an email will be sent to the administrator only for non-confirmed reservations).