When computers and other devices are connected together in order to share data and communications then a computer network has been built.
There are many aspects that characterize computer networks. One is the size of the network. A network can be considered a local area network if it covers a small geographic area such as a building. Wide area networks typically cover areas larger than a local area network and may comprise a college campus or a company with several buildings in one location. Metropolitan area networks, on the other hand, usually cover wide geographic areas such as a city, a county or entire state.
Networks can be categorized according to their topology which represents their layout or structure. One topology is called a bus in which all devices on the network communicate through a common conduit while another is a star in which all communications are controlled by a centralized device. Other topologies include ring and mesh.
Devices on a network can be connected together by various means. The most popular of these media include twisted-pair copper wire, fiber optics, coaxial cable and wireless technologies. Wireless technologies are becoming more popular these days with the widespread use of smartphones and have found their way onto many college campuses to provide connectivity to students and faculty anywhere on campus. Many local retail establishments also provide wireless connections for their customers.
Networks also need a protocol or a set of rules that all devices use for communicating with each other. One popular protocol is TCP/IP which is used for all communications on the Internet and for most networks in private businesses and corporations.