Some conference calls are set up where the calling party calls the other participants and adds them to the call, and in some cases the other participants call into the conference call, either by dialing into a "conference bridge", a specialized type of telephone that answers multiple calls, or by using a special telephone number set up for that purpose.
Conference calls can be used for entertainment or for commercial dating services, such as the party line. People call in to a specified telephone number which allows them to talk to others, serving as a way to talk to and perhaps subsequently meet new people. Conference calls are most commonly used by businesses.