The network is the word we hear everyday life. The network is a system where we can share information and work together to be together. Suppose, for example, deliver the letter to the Post Office in whole country. So post office has networking system all over the country. In this network, they have much office in different places in our country & they have some rules and regulations. Post office can run by following this rules and regulations. If post office has not such kind of networking system they cannot do anything. In case of computer, such kind of network is being used. When one computer is connected with more than one computer and they exchange their information then it is called a part of network of this computer. To make networking two computers is needed. A special device is used to connect one computer with another. Networking is used to make easy of our everyday life tasks. When we connect one computer with another they can share their resource with each other. Here resource means information & hardware device. Before using network, this was very difficult to share information with one computer to another. In the network of computer, one is sender & another is receiver. Sender computer is that computer who sent information to another computer. To build network in a computer is not main function. If there is any computer, printer or any device which exchange information, is called Node or Device. To exchange information with each other there is needed a medium. Almost every case, cable is used to connect devices. In a long cable, many devices are to be included. This cable is made by copper. Otherwise plastic and glass is another medium which is used. This cable is connecting with device by using an air medium. This is done by radio or microwave transmission. When more than one network is connected with other, then it is called internetwork. If different types of hardware or software is used to connect network with other then it is called internetworking. On the basis of function and structure, network can be classified into three types. They are LAN (Local Area Network), MAN (metropolitan Area Network) & WAN (Wide Area Network). Among them LAN is widely used. In the world of networking technology is changed very rapidly. Nowadays internet is very popular network. To connect every device with this network, there is going on much research. Recently it could be possible. Then no device will remain outside of network.