Firstly some history. The forerunner of the Internet was the ARPAnet. The network was modelled on a source and a destination computer with an unreliable network in between. The computers, not the network were responsible for establishing that the information was exchanged. At about the same time as the Internet was developing the technology called Ethernet was also being developed.
Ethernet is a protocol and transport system for information using coaxial cable.
A demand was created to interconnect the Local area networks, connected via an ethernet system, into the ARPAnet to share computer facilities. All these networks and computers were growing using IP as the protocol. An aside is probably important at this time to explain in some more detail what exactly is a protocol. Basically a protocol is an agreed method of exchanging information. A computer protocol is analogous to a phone conversation between two parties.