While there are a lot of habitancy out there using electronic mail as one of their original forms of communication, there are not very many who know much about what an email server is. If this is the situation that you are in, then you are not alone. However, the basic conception is not all that hard to understand. The following should furnish a slight more insight.
To begin, an email server is a program that is designed to properly send, receive, and route any messages. This means that yours will send your message for you, make sure it gets to the right place, and make sure that you get your incoming messages. That is exactly what it is designed to do. As previously mentioned, a rather straightforward concept. However, the programming for this is not as simple, and that is why it is not going to be described here. It boils down to just a bunch of technical jargon that is designed for those who do programming to understand.