Fourth rail

Okay kiddo, so you know how trains run on tracks, right? Well, sometimes there is a special extra track called the "fourth rail." It's not always there, but when it is, it's usually located right next to the other tracks that the train is running on.

The fourth rail is a bit different than the other tracks, because it has a special job. You see, the other tracks carry electricity that helps power the train. But the fourth rail carries a different type of electricity that is used to power things like lights and air conditioning on the train.

Now I know that might sound a bit confusing, so let me try to explain it another way. Imagine you're in your bedroom and you want to turn on your lamp. You need to plug it in to the wall, right? Well, the fourth rail is kind of like the wall outlet for the train. It provides the electricity that powers all the things that make riding the train more comfortable for passengers.

So, to sum it up, the fourth rail is a special track that carries electricity that powers things like lights and air conditioning on trains. It's like the wall outlet in your room that lets you plug in your lamp. Cool, huh?