Okay kiddo, a boxcab is a special type of train engine that looks different from regular train engines. It has a box-shaped body with two small windows on either side and two big front windows for the driver to see out of.
The reason why it looks like a box is that inside there is a big motor that powers the train, and it needs to be protected from the wind and elements. The two smaller windows on either side are for the driver and engineers to look out of and see what's going on.
The boxcab engine is also very efficient because they can use a lot less fuel to power the train compared to older engines, which is good for the environment. Some people also think they look super cool too!
Overall, a boxcab is like a shape-shifting robot train that has a big motor inside and looks super futuristic. So if you ever see one, make sure to wave hello to the driver and appreciate its unique design!