How was the internet first invented without the internet?
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If you have two computers in the same room, it’s easy to connect them together. You just need a couple wires.
If you want to connect a few computers together, you can connect them all to the same wire, but they need to have some clever logic to share the wire. (For example you could carefully assign every computer a time when they’re allowed to talk. Or you could just have each computer talk whenever it has something to say and no other computer is talking, then if two computers try to talk at the same time, both stop talking and wait a random time until trying to talk again.)
To be sure each computer has time to talk, they should do their transmissions in short bursts called “packets.” If you want to have a long conversation, like sending a big file, you can send as many packets as you want — hundreds, thousands, millions, whatever it takes. You can also assign each computer a number (“network address”), and add some extra information to the beginning of the packet (“packet header”) to tell you which computer that packet is coming from and going to. Of course you need a detailed engineering spec (protocol) to tell you what this data looks like, how it’s organized, and the lower-level electrical signaling — the protocol is the “language” of the network.
If you want to connect a lot of computers together, perhaps over long distances, a single wire doesn’t work any more. At this point, you need to divide the system into several wires, then have one computer (“router”) attached to all the wires. The router will move packets between the wires based on information in the packet header.
If you want to connect even more computers together, it gets too hard to have all the wires connect to the same place. Now you need multiple routers, and have the routers connect to each other. In a very large network it’s not even possible for all the routers to connect to the same place, so a packet headed to a faraway wire will usually be able to get to its destination, but it will need to take an indirect path through multiple routers.
After a while a bunch of different companies / universities / governments all have networks like this, and some of them want to connect to each other.
Problem: Each has its own “languages” (protocols) and way of assigning numbers to computers (network addresses). And nobody’s willing to change their network, because it would be expensive and disruptive.
Solution: Make a new protocol and scheme for assigning numbers to computers. Then have each network add a router that speaks both the new protocol and the network’s existing protocol. Put the new protocol’s packet headers inside the existing network’s packets. Now everybody can talk to other networks over the new protocol, and nobody had to do a bunch of expensive and disruptive changes to their existing network.
Now we need a name for what we’ve done. Whenever we’re INTER-connecting a bunch of NET-works, let’s call it an INTER-NET for short. Except when you have multiple inter-nets, it seems that quite often somebody will connect those multiple inter-nets to each other. So really you end up with one giant inter-net that connects most of the world’s computers: The Internet.
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