Have you ever played with toy cars, and some of them have train tracks that they can drive on? Well, imagine if a car was actually made to drive on those kinds of tracks. That's kind of what a Decauville automobile is!
A Decauville automobile is a special kind of car that was built to drive on rails like a train. It was made in France a long time ago, in the early 1900s. The reason why people made these cars was because they needed a way to transport things like coal and other heavy things from one place to another.
Now, you might be thinking, "Why not just use a train?" Well, sometimes the places where they needed to take these heavy things to were too hard to get to with a train. That's where the Decauville automobile comes in!
This car was small and light enough to drive on the rails of a train track, but was still powerful enough to carry a lot of weight. Think of it like a big, heavy-duty truck that can drive on the train tracks instead of on the road.
So, to sum it up, a Decauville automobile is a special car that can drive on train tracks and was used to transport heavy things like coal back in the olden days.