What Is the Internet?

The Internet is a global system of interconnected computer networks that use the Internet Protocol suite (TCP/IP) to communicate across diverse physical media and administrative boundaries. It consists of hundreds of thousands of autonomous networks operated by governments, universities, corporations, and internet service providers, bound together by shared addressing conventions, routing protocols, and application-layer standards. Any device assigned an IP address and connected to a participating network can exchange data with any other reachable device, a property that distinguishes the Internet from earlier proprietary wide-area networks.

The Internet traces its operational roots to ARPANET, the experimental packet-switched network funded by the US Defense Advanced Research Projects Agency in 1969, which demonstrated that computers at geographically separated sites could communicate reliably by dividing data into packets and routing them independently. The transition from ARPANET to the modern public Internet accelerated through the 1980s as the TCP/IP protocol suite was standardized, the domain name system (DNS) was introduced, and commercial network providers began interconnecting with the research backbone.

Network Architecture and Protocols

The Internet's architecture is built around the TCP/IP protocol stack, in which the Internet Protocol (IP) handles packet addressing and routing across heterogeneous networks while the Transmission Control Protocol (TCP) provides reliable, ordered delivery to applications. IP version 4 (IPv4) provided the original 32-bit address space; its successor, IPv6, extends addressing to 128 bits to accommodate the growing number of connected devices. Routing protocols, including the Border Gateway Protocol (BGP) for inter-domain routing and OSPF for intra-domain routing, determine the paths packets follow across the network. Quality-of-service architectures such as Differentiated Services (DiffServ) and Integrated Services (IntServ) allow network operators to prioritize certain traffic classes, a necessity for real-time applications including voice over IP and video conferencing. The IETF's repository of RFCs documents the technical specifications for these protocols; RFC 791 (IPv4), RFC 793 (TCP), and RFC 2460 (IPv6) remain foundational references. Multiprotocol Label Switching (MPLS) adds a label-switching layer that enables traffic engineering and the construction of virtual private networks across shared infrastructure.

The World Wide Web and Online Services

The World Wide Web, introduced by Tim Berners-Lee at CERN in 1989 and publicly accessible from 1991, is an application layer built atop the Internet that organizes information as hyperlinked documents retrieved via the HTTP and HTTPS protocols. While the Web is the most widely used Internet application, the Internet itself encompasses many additional services: email (SMTP, IMAP), domain name resolution (DNS), file transfer (FTP), real-time messaging, and peer-to-peer protocols. Streaming media platforms use adaptive bitrate protocols such as MPEG-DASH and HLS to deliver audio and video at quality levels matched to available bandwidth. Electronic commerce relies on TLS-encrypted connections, payment gateway integrations, and certificate authority infrastructure that the Internet's application layer provides. The Internet Society's overview of Internet infrastructure describes how these services relate to underlying network operations and how governance bodies coordinate the allocation of IP addresses and domain names.

Virtual Private Networks, Extranets, and Enterprise Connectivity

Organizations connect to the Internet through arrangements that balance openness with security and access control. Virtual private networks (VPNs) encrypt traffic between endpoints and tunnel it through the public Internet, allowing remote workers and branch offices to access enterprise resources as if they were on a private network. Extranets extend a subset of an organization's intranet to specific external partners, suppliers, or customers under defined access policies. Service Level Agreements (SLAs) between enterprises and their internet service providers define parameters such as uptime guarantees, round-trip latency limits, and bandwidth commitments. Wireless communications, from cellular 4G and 5G networks to Wi-Fi and satellite broadband services, have extended Internet access to mobile and rural contexts. The IEEE Internet Technology Policy Community coordinates engineering community engagement on policy issues including network neutrality, spectrum allocation, and security standards that shape how Internet infrastructure is designed and governed.

Applications

The Internet has applications in a wide range of disciplines, including:

• Electronic commerce and digital payment systems
• Open data publishing and access to scientific datasets
• Industrial IoT and sensor network monitoring
• Distance education and remote collaboration platforms
• Smart city infrastructure including traffic management and utility monitoring