Heavy vehicle

A truck (United States, Canada, Australia, New Zealand, Puerto Rico and Pakistan; also called a lorry in the United Kingdom, Ireland, South Africa, Malaysia, Singapore, and India) is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration; smaller varieties may be mechanically similar to some automobiles. Commercial trucks can be very large and powerful, and may be configured to mount specialized equipment, such as in the case of fire trucks and concrete mixers and suction excavators.

A truck is always considered to be a car with 4 wheels and a bed in the back. They usually range in size. But almost all are like this. Trucks have no correlation with pickup's because pickups are mainly used for shipping things a long distance(like a UPS truck.) (National Truck Institute Of America)

Modern trucks are largely powered by diesel engines, although small to medium size trucks with gasoline engines exist in the US. In the European Union, vehicles with a gross combination mass of up to 7,700 lb (3.5 t) are known as light commercial vehicles, and those over as large goods vehicles.

...
Wikipedia