What is Asterisk?
As the most popular open source communications project, Asterisk provides a feature-rich voice communications server. Being able to deploy a variety of telephony applications and services, including PBXs, Gateways, Call Centre and IVR Systems.
As a PBX, Asterisk is the core of an IP telephony system, switching calls, managing call routing and enabling features that you would expect from a telephone system. Running on a variety of operating systems including Linux and Mac OS X, Asterisk provides many advanced features that are often associated with high end (and subsequently high cost) telephone systems. Designed for maximum flexibility, supporting VoIP in many protocols and can interoperate with almost all standards-based telephony equipment using relatively inexpensive hardware.