Basically, it is a collection of two or more computers and associated devices that are linked together with communications equipment. Once connected, each part of the network can share the software, hardware, and information contained in the other parts.

The most common types of network are LANs (Local Area Networks, in which the computers share the same office space, room, or building) and WANs (Wide Area Networks, in which LANs are connected at different geographic locations by telephone lines or radio waves, as in wireless communications). There are some other types of computer networks, including:

• campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base.
• metropolitan-area networks (MANs): A data network designed for a town or city.
• home-area networks (HANs): A network contained within a user's home that connects a person's digital devices.

In addition to these types, the following characteristics are also used to categorize different types of networks:

• topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring.
• protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network .
• architecture : Networks can be broadly classified as using either a peer-to-peer or client/server architecture.

Network connections are established by twisted-pair cable, coaxial cable, fiber-optic cable, connectors, or NICs (network interface cards).

Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers.