Networking basically means communication between two or more entities. The communication can be between two humans or two machines. Also the distance involved between the entities may be from a few metres to thousand of kilometres. Depending upon the distance and the number of communicating entities various types of networking models have been developed.

The existence of Networks dates back to the 19th century with the world's first telecommunication giant “ The Western Union” setting up the overland telegraph lines in the 1860's accross the US. After the telegraph, telephone was introduced when Bell telephones began operation in the late 1890's. In telegraphic communication only characters could be sent while a telephone allows only voice. With the advent of computer networking one could sent while text , audio, image, as well as video signals through the same communication channel. Computer networks are used in small / large offices , banks, government organisations, college campus, libraries , railway/ airlines booking offices etc.

A computer network is formed when two or more computers or devices connected by cables or wireless communication can communicate with each other and exchange information.

Every computer connected in a network is called node. The connected computers can be located within a small geographic location like an office space or they can be spread over long distances like different branches of an office located in different cities. Special network software allows the computers to communicate over the network using special rules called protocols.

• Why use Computer Networks?

A computer network can provide several benefits over standalone computers, like : 

1. Network Resource Sharing : A network may be used to share expensive peripheral devices such as laser printers, large removable storage drives, CDROM servers, modems etc.
2. File Sharing : Networks let sharing of files between different computers. The sharing can be between any two computers , or from servers that store common files shared by other computers.
3. Application Program Sharing: Common application programs can be loaded in servers , which are then shared by other computers in the network. This saves disk space and helps in upgrades of the application programs in one computer only.
4. Fault Tolerance : This is the ability of a system to function even in case of an error in the system. If a computer in a network fails another computer can take over the processing.
5. Data Backup : Data from different networked computers can be backed up in a central computer or a sharable mass storage device.
6. Better Communication : Applications like email, net-meeting etc. allow workgroup members to communicate among themselves.

However , certain disadvantages need to be considered that include:

1. Central Control : For a server based network , the network system fails if the main server fails .
2. Security : If network security is not strong , unauthorised people may access confidential data.
3. Spped : Application programs that run from a server may tend to be a little slower depending on the processing capacity of a network , as multi copies of the same program has to run.