A computer network is a group of devices connected with each other through a transmission medium such as wires, cables etc. These devices can be computers, printers, scanners, Fax machines etc. The purpose of having computer network is to send and receive data stored in other devices over the network. These devices are often referred as nodes.
I have covered each topic of Computer Network in separate tutorial and provided the link of all the tutorials below in a systematic manner. You can go through the complete computer network tutorial in the given order to have better understanding of the topic.