What is asterisk really?
Asterisk is a free open-source VOIP platform from Digium - the name comes from the term "wildcard" which refers to anything and everything. So no matter what system , protocol or platform you have , asterisk can interface with it. Solutions like FreePBX , Trixbox and Elastix - to name only a few , might be asterisk-based but it not truly asterisk and still have many issues , but using raw asterisk is stable , robust and most powerfull. This means that you can create your own IP-PBX using a Normal server and a PSTN gateway or build a Home Automation system that can switch lights on/off telephonically or build a VOIP platform and sell airtime to your clients and much more - but do it yourself !