A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Networks are commonly categorized based on their characteristics. In computer networks, computing devices exchange data with each other using connections (data links) between nodes. These data links are established over cable media such as wires or optic cables or wireless media such as Wi Fi.
Network nodes are network computer devices that originate, route and terminate data. Nodes are generally identified by network addresses, and can include hosts such as personal computers, phones, and servers. As well as networking hardware such as routers and switches. The two devices can be said networked together when one device is able to exchange information to the other device. Whether they have a direct connection to each other or not. In most cases, application specific communications protocols are layered (i.e. carried as payload) over other more general communications protocols. This formidable collection of information technology requires skilled network management to keep it all running reliably.
With computer networks we support an enormous number of applications and services such as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers, printers and fax machines. As well as the use of email and instant messaging applications and others. The best known computer network is the Internet.

Computer networks differ in:

  • Transmission of medium used to carry their signals.
  • Communications protocols to organize network traffic. 
  • Network size, topology, traffic control mechanism and organizational intent.  

We use computer networks to:

  • Facilitate communication via email, video conferencing, instant messaging etc.
  • Enable multiple users to share a single hardware device like printer or scanner.
  • Enable file sharing across the network.
  • Allow sharing of software or operating programs on remote systems.
  • Make information easier to access and maintain among network users.

There are many types of computer networks:

  • Local Area Networks (LAN).
  • Personal Area Networks (PAN).
  • Home Area Networks (HAN).
  • Wide Area Networks (WAN).
  • Campus Networks.
  • Metropolitan Area Networks (MAN).
  • Enterprise Private Networks.
  • Inter networks.
  • Backbone Networks (BBN).
  • Global Area Networks (GAN).
  • Internet.