There are many networks in the world, some are natural, and some are man-made. There is a network of veins and arteries in the body and there is a network of railroads. But these days when we say networks, we mean data communication networks. Data communication is the movement of computer data from one computer to another. The data may travel as an electrical or an optical signal on transmission systems. Such systems are called data communication networks or simply network. Networking helps us in getting the information fast. there are various types of computer networks, which are not known to many adult learners and adult educators. According to Tanenbaum (2007), these networks include LAN, MAN, and WAN.Local Area Network (LAN):A local area network connects computers that are in the same building. A network spread over a few kilometers also comes under LAN.The LAN is usually realized using Ethernet technology or token ring technology. Fiber Distributed Data Interface (FDDI) is also becoming popular. The transmission rate varies from 10 Million bits per second to 1-gigabits per second (10Mbps-1Gbps). A computer has a network interface card such as an Ethernet card that connects it to the network circuit.Usually, LAN is under the control of a single organization. The prime objective of LAN is to facilitate information and resource sharing within an organization. For instance, application software which is used by many people in the organization can be installed on a computer. This computer is connected to another computer by LAN and everybody can use the same software. Metropolitan Area Network (MAN): a Metropolitan Area Network (MAN) is basically a bigger version of LAN and normally uses similar technology.It might cover a group of nearby corporate offices or it can be in a city.It can be a private or public network. Wide Area Network (WAN):A wide area network connects computers in different cities or countries.The network to connect computers that are thousands of miles apart is not built by an organization. Instead, the organization uses leased telephone lines.It is owned and managed collectively by many cooperating organizations. Hence, WAN covers the largest area and LAN covers the smallest area.