To communicate is one of the basic skill that mankind have been practicing since the origin. The only thing that kept changing was the medium used to communicate. We have evolved a lot in ages and now we can effectively communicate with people from anywhere in the world and even outside the world. There are different advanced forms to do it but when you burn them all to ground the ultimate idea is to exchange information between a sender and a receiver by connecting them via a medium that depends on area that separates them and mode of communication they prefer. It was simply classified as LAN (Local Area Network), WAN (Wide Area Network) and MAN (Metropolitan Area Network) decades ago. But we now have a more classified system based on the enormous advancement in technology.