The word Internet comes from Interconnected Network. The networks are things that are connected together. So a computer network consist with a two or more computers who are linked together. The simplest computer network maybe is to connect two computers with a cable. If we simply add other twoc computers and connect their network too under the same rules who applies for our network.. Here it is an interconnected network.
At this moment the internets is made of billions of computers and devices all over the world and all of them are interconnected. That means that if I take a picture of my cat in London you can see that picture in almost no time when you are in Aruba for example.