A network is a system of computers and other devices connected for the purpose of data/information exchange, and consists of hardware and software. Hardware on a network includes physical devices such as the computer itself, printers and file servers. These are commonly referred to as nodes on a network.

Unless the nodes are connected to one physical cable, which is unlikely and inefficient, software devices must be used to connect the nodes and share information effectively. A network bridge connects network cables without making decisions as to the best route for a message to take. Alternatively, a router contains addressing and routing information that decides from a message’s address the most efficient route to take. A message can be passed from router to router several times before being delivered to its destination.

For nodes to exchange data, they must use a common set of rules defining the format of the data and the method in which to transmit it. A protocol is a formalized rule set regarding the exchange of data and the interactions between the network nodes. A router connects networks only if they are using the same protocol and formats. To communicate between networks with differing protocols and address formats a gateway is needed. The gateway converts addresses and protocols to connect dissimilar networks.

Networks connected by routers or gateways are known as an internet. For this reason the term ‘Internet’ (capitalised) is used to refer to the largest global system of networks, also called the Worldwide Internet. The basic protocol for implementation of the Worldwide Internet is called the Internet Protocol (IP).