Computer networking consists of a set of protocols and practices designed to allow devices to communicate with each other. The Internet is likely the computer network you know best. But what is it, really?
The word "Internet" comes from the shortened word internetwork, and it was originally developed by the U.S. Department of Defense. Today, the Internet is made up so many connections it's almost impossible to imagine. By connecting to it, you can access the largest repository of human information ever maintained. Further, you can communicate with anyone connected to the network near-instantly, anywhere in the world. It is nothing short of incredible that humans have and continue to pull off this project.
If you want an idea of what the Internet looks like logically, check out The Internet Map.
Of course, the Internet is hardly the only network out there. Networks come in all shapes and sizes. There are big networks called Wide Area Networks (WANs) and small ones called Local Area Networks (LANs). If you're reading this webpage over the Internet right now, you're likely connected to both kinds.