Trains are a mode of transportation that allow for quick and efficient travel over long distances. They consist of a locomotive, which provides the pull for the train, and several connected cars which can be for transporting materials, food, animals, or even people. They're driven by steam power across parallel tracks that are laid from town to town and even across continents.
Automobiles are a similar idea, but without the tracks, and only individual cars. And every car contains an engine as well as a steering wheel. They're sometimes called "horseless carriages" as well, since they were based on horse-drawn carriages originally. They allow a greater range of movement than trains, but are slower and less efficient. However they are much more complex machines since they are smaller and because of their ability to steer.