A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle designed to carry many passengers.[from wikipedia]

Also called a car

A single-track, two-wheeled motor vehicle

A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction.[from wikipedia]

A truck (or lorry) 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.[from wikipedia]