Okay kiddo, so imagine a train that's not as big as the regular trains you see. This smaller train is called a narrow-gauge railway.
In Britain, there are a lot of places where these trains were used to transport things like coal, milk, and goods from one place to another.
The tracks that these trains run on are closer together compared to regular trains. This is because the trains are smaller and need a smaller track to run on.
People also use these trains to travel to scenic parts of the country, like mountains and forests.
Narrow-gauge railways are important in Britain because they helped connect different parts of the country and made it easier for people to transport things.