Vroom, vroom! A truck is a motorized vehicle on wheels—it's like a car, but bigger. Trucks are often used for hauling or transporting things.
What we call a truck in the U.S. is generally called a lorry in the U.K. Trucks vary in size from small pickups that aren't much larger than cars to 18-wheel semi-trailer trucks. These big trucks are built to transport heavy goods and are mostly powered by diesel fuel. Truck is also a verb, meaning "convey by truck" or "proceed leisurely." The Middle English root word means "wooden wheel."