The Internet is a vast collection of computers linked by cable and satellites, not controlled by any one authority, but all operating under common network protocols. The term ‘Internet’ includes both the hardware (satellites, cable, routing devices and computers) and the software (programs and network protocols) that enable computers to communicate with each other.

When information is sent across the Internet, the Transmission Control Protocol (TCP: the networking-language computers use when communicating over the Internet) first breaks the information up into packets of data. The client computer sends those packets to the local network, Internet service provider (ISP), or online service. From here, the packets travel through many levels of networks, computers, and communications lines until they reach their final destinations. Many types of hardware help the packets on their way. These are:

Hubs, which link groups of computers together and let them intercommunicate through multiple ports.
Bridges, which link local area networks (LANs) with each another.
Gateways, which act like bridges, but also convey data between dissimilar networks.
Repeaters, which amplify the data at intervals so that the signal doesn’t weaken.
Routers, which ensure packets of data arrive at their proper destination across different technologies, media, and frame formats.
Servers, which deliver web pages and other services as requested.
Client computers, which make the initial request for Internet services, and run applications to handle those services.
Cables and/or satellite communications, which make the hardware connections.

All hardware units need common operating methods, basic instructions called protocols that specify to all parties how the data will be handled.