Push–pull train

Okay, so imagine you have a bunch of train cars all connected to each other like a big choo choo train. Normally, the train engine pulls the cars along the tracks, right? But sometimes, for various reasons like safety or convenience, the engine needs to be at the back of the train instead of the front.

That's where the push-pull method comes in. In a push-pull train, there's an engine on both ends of the train. The first engine pulls the train as usual, while the second engine pushes it from the back. So when the train needs to go backwards, the engines just change places and the rear engine becomes the one that pulls the train.

It's like when you and your friend are trying to move a heavy object. Normally, you would both be on one side, pulling the object towards you. But if you need to move the object in the opposite direction, one of you would have to go to the other side and start pushing instead of pulling. That's kind of like what a push-pull train does!