The internet is a worldwide system of interconnected computer networks that communicate using standardised networking protocols, principally the Internet Protocol Suite, commonly called TCP/IP. It is not a single machine, network, company, or physical object. Instead, it is a distributed infrastructure made up of millions of private, public, commercial, academic, governmental and other networks that are interconnected and can exchange data. Computers, servers, smartphones, routers, switches, data centres, cables, radio systems, satellites and other devices participate in this infrastructure.
The word internet is derived from “internetwork”, referring to networks connected together. The defining characteristic is interoperability: independently operated networks can communicate because they agree to use common protocols and addressing conventions. This enables information to travel between devices even when those devices are owned by different organisations, use different local technologies, or are located on opposite sides of the planet.
At a technical level, the internet operates as a packet-switched network of networks. Applications generate digital information, which networking software divides into packets or otherwise represents as units suitable for transmission. These packets are given addressing and control information and are forwarded through networks using routers. The Internet Protocol provides addressing and packet delivery across interconnected networks, while protocols such as TCP provide reliable, ordered delivery when an application requires it.
Other transport protocols, particularly UDP and increasingly QUIC, support different performance characteristics. At the lower layers, packets can travel through Ethernet, Wi-Fi, fibre-optic systems, cellular networks, cable networks, satellite links and numerous other technologies. The internet therefore does not depend on one physical transmission medium. It is an abstraction that allows many different underlying networks and technologies to participate in one interoperable global system.
Internet connectivity depends on a hierarchy and interconnection of networks rather than one central authority controlling every connection. An ordinary home connection may involve a device connecting through Wi-Fi or Ethernet to a local router, which connects to an Internet service provider. The provider's network may connect to regional networks, Internet exchange points, transit providers, content networks and other autonomous systems before traffic reaches its destination. Routers make forwarding decisions based on destination IP addresses and routing information.
The Border Gateway Protocol is particularly important for exchanging reachability information between independently administered autonomous systems. This decentralised architecture allows traffic to take different paths and permits networks to join, leave, expand or reconfigure without redesigning the entire internet. There is consequently no single “main internet cable” or central computer through which all Internet traffic passes.
The internet supports many different services because networking infrastructure is separated from the applications that use it. Web browsing is one major application, but the internet also carries email, instant messaging, voice and video communications, online gaming, file transfer, remote administration, cloud computing, software updates, streaming media, financial transactions, Internet of Things communications and many other activities. A service generally operates through application-layer protocols that use the underlying Internet Protocol Suite.
For example, the web commonly uses HTTP or HTTPS, email can use SMTP and related protocols, and the Domain Name System translates human-readable domain names into information used to locate Internet services. This separation is fundamental: the internet provides general-purpose connectivity, while individual services define how particular types of information are requested, transferred, interpreted or exchanged.
The physical internet consists of infrastructure distributed across continents and oceans. Fibre-optic cables carry enormous quantities of traffic through terrestrial routes and submarine cables, while copper-based access networks, coaxial cable systems and wireless technologies provide other forms of connectivity. Large data centres contain servers and networking equipment, and content delivery networks place frequently requested data closer to users. Internet exchange points allow participating networks to exchange traffic directly, potentially reducing reliance on third-party transit.
Mobile operators connect cellular users into wider IP networks, while satellite systems can provide connectivity where terrestrial infrastructure is difficult to deploy. The physical paths are owned and operated by many different organisations, including telecommunications companies, governments, universities, cloud providers, content providers and infrastructure companies. The global internet is therefore simultaneously a logical system of protocols and a vast collection of physical infrastructure.
Several concepts associated with the internet are often confused. An Internet service provider is an organisation that provides customers with Internet connectivity, but it is not the internet itself. A router forwards network traffic between networks, but it is only one type of component within the larger system. The World Wide Web is an Internet service rather than a synonym for the internet.
A website is a collection of web resources made available through web technologies, while the internet provides the underlying connectivity that allows those resources to be reached. Cloud computing also relies heavily on the internet but is a computing model rather than another name for the network itself. Similarly, Wi-Fi is a local wireless networking technology; connecting to Wi-Fi does not inherently mean that the Wi-Fi network itself is the internet. These distinctions are important because the internet is fundamentally the underlying interconnected networking infrastructure and protocol system on which many higher-level services operate.
The modern internet developed from earlier computer networking research, particularly work on packet switching and interconnecting heterogeneous networks. ARPANET, funded by the United States Advanced Research Projects Agency, became an important early packet-switched network and demonstrated practical networking between geographically separated computers. The development of TCP and IP provided a general mechanism for connecting different networks, leading to the transition from individual network environments towards an internetworked architecture.
The Domain Name System, developed in the 1980s, made it more practical to use names rather than numerical addresses. During the 1990s, commercial Internet access expanded substantially as restrictions on commercial use diminished and public Internet service providers emerged. The subsequent spread of personal computers, browsers, mobile devices, broadband and cloud services transformed the internet from a largely specialist research and communications infrastructure into a globally pervasive platform.
The internet today is characterised by scale, decentralisation, redundancy and continuous change, but it is not inherently synonymous with openness, anonymity or unrestricted access. Governments, network operators and organisations can impose technical or legal controls, while firewalls, filtering systems, authentication mechanisms and content restrictions can limit connectivity or access to particular resources. Internet traffic can also be monitored or exposed depending on the protocols, network position and security measures involved.
Encryption technologies such as HTTPS, virtual private networks and end-to-end encrypted applications can protect particular communications, but they do not make every aspect of Internet activity inherently anonymous. Performance is also variable: bandwidth, latency, packet loss, congestion and routing distance can affect applications. The internet's significance comes from its ability to provide interoperable global connectivity rather than from any particular application, device or access method.
