This is the application itself. It contains the code and the user interface.
Trainz is a complex simulation meant for a keyboard and mouse (or a full rail driver controller). Trying to navigate complex switches, brakes, and throttle controls via a touchscreen interface is clunky. The on-screen buttons often obscure the beautiful scenery you are trying to admire.
Move the folder (usually named com.n3vgames.android.trainz ) to the following path: Internal Storage > Android > obb .
Use a file manager (like ZArchiver) to unzip the OBB data.