A conference bridge allows a group of people to participate in phone call. The most common form of bridge allows participants dial into a virtual meeting room from their own phone. Meeting rooms can hold dozens or even hundreds of participants. This is in contrast to three-way calling, a standard feature of most phone systems which only allows a total of three participants.
Asterisk includes a standard application called ConfBridge. ConfBridge is a high definition-capable conference bridge component that makes it easy to build stand-alone conferencing services or to integrate conferencing into other solutions, including IP PBX systems.
Creating a conference room is trivial, requiring only a few lines of Dialplan script. ConfBridge includes a wealth of administrative features (mute participants, add / remove callers, etc.) and a rich event structure that allows developers to build fully integrated user interfaces. ConfBridge also supports basic video conferencing, though this feature is currenly considered experimental.http://discuss.eduguru.in