Explain · Like I'm five version
The internet in terms of Royal Mail
The internet is just like the Royal Mail but with magic letters that fly through invisible wires instead of red vans.
When you send a message, it is like popping a postcard into a tiny postbox. Your computer breaks your big picture or long story into millions of little envelopes called packets. These packets have your address and the person you are writing to written on the front, just like a stamp. A busy worker in a sorting office looks at the zip code and decides which road the letter should take. Some packets might take the train, some might take a plane, and some might get stuck behind a slow tractor on a country lane.
Once all your little envelopes arrive at the other person's house, a special machine puts them back together in the right order. It is just like building a Lego castle from a big pile of bricks. If a piece goes missing, the system sends a polite note asking for that one specific brick to be sent again. Eventually, the whole picture is finished and your friend sees exactly what you sent. It is much faster than waiting for a birthday card from your nan, but it uses the same sorting office logic.
The internet never actually closes for the night or takes a break on a bank holiday. It just keeps sorting and delivering your digital parcels while the real postmen are fast asleep in their own beds.
Where the analogy breaks downReal mail does not arrive at the speed of light, and you rarely lose a birthday card because a stray bit of code got confused in a server in Leeds.