WHAT IS COMPUTER NETWORK?

Computer Network is a telecommunication network that enables sharing of resource  and information . In other way Network can we defined "as group of computer that are connected with media link" .  media links may be wired or may be wireless. For transferring data different PROTOCOL are used. And data are transferred in the form of Packets.

                       basic fig of connection of computer to internet 

As you are seeing a device router is used here. The basic work of router is to connect devices to different Network. In figure the router are used to connect computer from Internet.