Okay kiddo, picture a really long train with many train cars connected together, like the ones you see in storybooks. Now imagine one of those train cars has an engine inside that can pull the train without needing a separate locomotive. That car is called a "motor coach"!
Instead of sitting in separate seats like on a regular train, the motor coach is like a big room on wheels with lots of seats facing each other. It's like a really long bus but on train tracks.
The rail motor coach is used to transport people on a railroad, the same way a regular train would. But it can go where normal trains can't go, like on smaller rails and at a slower speed.
It's a fun way to travel because you get to ride on a train but in a different kind of train car that feels more like a big room, and you can see really cool views out the windows.