What Is a Network

A network is nothing more than machines that can send each other messages. Your laptop asking a web server for a page, a phone fetching mail, a backend service reading a database: all of it is one machine sending a message and another sending one back.

Those messages travel in small pieces called packets. A large response is chopped up, sent, and reassembled at the other end. You almost never deal with packets by hand, but it explains a lot of what you will see: why a slow connection delivers a page in fits and starts, and why some of a response can arrive when the rest does not.

The important habit for this course is to stop thinking of the internet as a place and start thinking of it as a conversation. Something asks. Something answers. Everything else is detail about who is asking, where they are, and what shape the question takes.

Those three details map exactly onto the next three chapters: addresses and names tell you where, ports tell you which program on that machine, and HTTP gives the question its shape.