What was ARPANET?

In 1983, DARPA decided that TCP/IP would be the standard set of protocols used by computers connecting to ARPANET. This meant that any smaller networks (for example, a university network) that wanted to connect to ARPANET also had to be using TCP/IP.

TCP/IP was available for free and was increasingly used by networks. The spread of TCP/IP helped create the Internet as we know it today - the network of networks that either use the TCP/IP protocols, or can interact with TCP/IP networks.