ISO 3166-2:GB is a fancy way of talking about a system that people use to tell where things are in a big country called the United Kingdom. It's like a giant map that shows all the different areas that make up the UK, like England, Wales, Scotland, and Northern Ireland.
The "ISO" part means that it's a special set of rules that everyone agrees to use when they want to talk about these places. "3166-2" is just a special code that helps people know which part of the UK they're talking about. When people add "GB" to the end, it just means they're talking about the UK specifically.
So why does this matter? Well, if someone is trying to send a package to a town in the UK, they need to know which part of the country it's in. And if someone is doing research on the UK, they want to make sure they're looking at the right information for the right part of the country. This fancy system just helps everyone stay organized and on the same page when they're talking about the UK.