Asterisk is a very large application that does many things. It can be somewhat difficult to understand, especially if you are new to communications technologies. In the next few chapters we will do our best to explain what Asterisk is, what it is not, and how it came to be this way. This section doesn't cover the technology so much as the concept. If you're already familiar with the function of a telephony engine, feel free to jump ahead to the next section.