Paypal appointments email question

When a customer makes an appointment when paypal is turned on :

1) customer clicks dates and hits submit
2) the paypal button shows up after

if the customer doesn't go to paypal and finalize his / her order what happens ?

Also, I notice the appointment is put in PENDING right away, without getting a callback from paypal. Does an email go out to the provider then ?
Or does it wait for a callback or successful payment ?