I'm not sure exactly what information your after, but a typical phone can setup a conference call either with an incoming call, or by placing an outside call. The user just hits the Transfer/Conference key, dials the third person, and then when the third person answers, hits the trans/conf key again.
There is an alternative method of setting up a phone to be auto answered whenever its called. So up to 7 parties can call it, and automatically be added into a conference. (Can't think of the official name at the moment though.)