Communication is essential in all aspects of businesses as well as in our daily lives. As the businesses started using computers for their business operations, the need to share and use information among employees and external parties became significant. The solution to this problem was setting up of a network which connected the computers and other resources for information and resource sharing among several users.

IT network or computer network allows linking several computers and other computing devices with each other to form a network, where the resources and data are easily shared among users; and, also allowing them to communicate with each other. The first primary operational network of the world was established for the United States Department of Defence. Nowadays, almost all businesses operate in a computerized environment, which is completely networked.

IT networks use a set of computer hardware devices and software programs. The IT networks can be classified in several ways. One way to do so is to categorize the networks according to the size of area they cover. The types include Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Campus Area Network (CAN), Storage Area Network (SAN) and Virtual Private Network (VPN). Businesses establish their networks according to the size, purpose and scope of the network that suit the specific requirements of the businesses.

Apart from this, the IT networks can be classified as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area Network (CAN), Storage Area Network (SAN), etc., depending on their scale, scope and purpose. Usage, trust levels, in addition to access rights, often fluctuate between these types of networks - such as, LANs tend to be designed for internal use by the internal systems of an organisation and by employees in individual physical locations (such as a building), while WANs may connect physically separate parts of an organisation to each other and possibly will include links to third parties.

IT networks may also be catalogued according to the functional relationships, which exist among the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.

Further networking of two or more networks altogether using common routing technology is called an Internetwork, which we generally know as internet. The basic structure connects several networks or network segments with devices, which operate at the network layer of the OSI Basic Reference Model (router). Internetworks can be classified into three classes depending on the types of users and administrators. These are the Intranet, Extranet and the Internet.

In present practice, interconnected networks utilise the Internet Protocol. There are at least three alternatives of internetworks, depending on who administers as well as who participates in them; Intranet, Extranet and Internet.

The technologies used may include galvanic cable, optical fibres or microwave links. A well-planned IT network is a necessity for all businesses and serves as the stepping stone towards success.