Lego 10875 is a train set that comes with a remote control app, allowing users to control the train's movement and complete fun activities. The app is compatible with specific Lego Duplo train sets, including 10874 and 10875. Users can download the app and follow the setup instructions to connect their device to the train. Once connected, they can use the app to drive the train, trigger sound effects, and interact with various action bricks placed along the tracks. The app also includes educational activities and challenges to enhance the play experience.