Put simply, Asterisk is a software-based PBX. By running Asterisk software, your PC can perform the functions of a PBX. Asterisk can also act as a gateway to public telephone network, a VoIP server, ACD server for call centers or IVR system.
Now that we answered "What", lets take a look at the other wives and the husband :-)
Who?
Asterisk was originally written by by Mark Spencer of Digium. However, it was released into open source under GNU General Public License (GPL) and therefore, owned and supported by the open source community. Digium is the company that provides commercial support and licensing to those who wish to extend Asterisk as closed source product.
Where?
Digium Inc is located in the United States.
When?
Asterisk was first created in 1999.
Version 1.0 was released in 2004.
Current version 1.8 was released in 2010.
How?
Asterisk itself is a set of software building blocks where you can configure and customise. It is not a turnkey solution. However, Digium does provide out-of-the-box Asterisk package that is easy to install and use.
One important point is that with Asterisk, you would still need to interface the hardware (ie. your PC) with the telephone system. This can be done in several ways. One way is to install T1/E1 interface card on your PC and connect them to the T1/E1 interface card of the PBX or direct to the carrier.
