It's an 0-4-0 (you knew that I'm guessing) side tank engine.
The side tank refers to the two water tanks on the side of the boiler.
If the water tank wrapped over the top of the boiler, that would make it a saddle tank (The water tank sits over the boiler like a saddle on a horse)
Despite the CNJ lettering, it's probably not an American prototype. While pretty generic looking, the smokebox front has a bit of a European look to it, as does the tapered smokestack. I'm not familiar enough with foreign engines to identify any specific prototype though...