It is a call which is made over internet protocol (VoIP). For example,
one can call using Google Voice to other recipient located miles away. Such
call can also be international.
Notification about the incoming calls, addressed to your land line or
office phone, coming to your cell phone. For instance, if you had a call to the
office at the moment when you were unavailable, a notification about the missed
call will come to your mobile phone.