British steam railcars were a type of train that was used a long time ago. They are different from regular trains because they didn't have a separate engine that would pull the carriages. Instead, the engine was built right into the carriage itself.
Think of it like a big, grown-up toy train. You know how you have those little cars that have an engine built right in and can drive around by themselves? It's kind of like that, but a lot bigger and more complex.
These steam railcars had a big boiler inside them, which was used to heat water until it turned into steam. The steam then went through pipes and into the engine, which made the wheels turn and the train move forwards.
It was a pretty cool way to travel back then because it meant you didn't need a lot of space to run the train. Instead of needing a big engine at the front of the train to pull it along, you just needed the railcar itself. So you could use smaller train stations and travel to places that might not have had big train tracks.
Steam railcars were most popular in the early 1900s, but as technology advanced, they were gradually replaced by more standard train engines. However, they are still remembered fondly as a fun and unique way to travel in the past!