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.
Feature allows subscribers calling to a certain number in order to connect to a conference call. The one, who dials the number, will connect to the conference. However as a conference controller one should give that certain number to all the participants and set the time for conference in order for the participants to be able to set up a successful conference.