A computer network or data network is a digital telecommunications network that allows nodes to share resources. In computer networks, networked computing devices exchange data between each other using a data link. The connections between the nodes are established using cable or wireless media.
Computer network devices that originate, route, and terminate data are called network nodes. Nodes can include hosts such as personal computers, telephones, servers, and network hardware. It can be said that two devices of this type are connected in a network when one device can exchange information with the other device, whether or not they have a direct connection between them. In most cases, application-specific communications protocols are layered (that is, transported as payload) over other more general communications protocols. This formidable collection of information technology requires specialized network management so that everything runs reliably.
Computer networks support a wealth of applications and services such as access to the World Wide Web, digital video, digital audio, application and storage server sharing, printers and fax machines, and use of email and instant messaging applications , as well as many others. Computer networks differ in the medium of transmission used to transmit their signals, communication protocols to organize network traffic, network size, topology and organizational intent. The best-known computer network is the Internet.