A truck is a vehicle usually used for transporting bulk goods, materials, or equipment. The word "truck" comes from the Greek "trochos", meaning "wheel".
In America, the big wheels of wagons were called trucks. When the gasoline-engine driven trucks came into fashion, these were called "motor trucks" and the Heavy Goods Vehicle (HGV)).
Lorry is a British term but is only used for the medium and heavy types, i.e. a van, a pickup or a SUV would never be regarded as a "lorry". Other languages have loanwords based on these terms, such as the Malay lori and the Mexican Spanish troca (or pickup in northern Mexico).
In Australia and New Zealand a small vehicle with an open back is called a ute (short for "utility vehicle") and the word "truck" is reserved for larger vehicles.