A collection of computers communicating with one another. It is composed of:

- Computers that may have one or many peripheral devices, as printers, scanners, and fax machines, attached.

- Devices that may be needed for network operation such as hubs, repeaters, and bridges.

- Communication medium through which computers communicate. The medium may be wires and cables or it may be open air and water.

- Software that provides services to network users and that implements the set of rules (protocols) each network computer must follow to be able to communicate with (understand) the others.

A network computer sending data to another is referred to as the source (sender or transmitter) and the one to whom these data are sent is referred to as the destination (receiver). A computer capable of sending or receiving data from a computer network is said to be online to the network otherwise it is offline. Networks allow users to share hardware, software, and data. Thus, they reduce cost, facilitate person-to-person communication, and enhance a company’s work performance