A steam turbine locomotive is like a really big train that runs on steam power.
You know how your bicycle moves when you pedal it? Well, the steam turbine locomotive works the same way, but instead of pedals, there is something called a turbine that is powered by steam.
The steam is made by boiling water, and that steam goes into the turbine. The turbine is kind of like a wheel with lots of little blades on it, and the steam spins that wheel really fast.
That fast-spinning turbine is connected to the wheels of the train, so when the steam makes the turbine spin, it also makes the train move.
Just like you have to keep pedaling your bike to keep it moving, the steam turbine locomotive has to keep making steam and spinning the turbine to keep moving.
It's a neat way to move a big, heavy train without using gas or electricity!