Tricycle

A tricycle is a vehicle with three wheels. It can be also called a trike. Tricycles can have pedals, an electric motor or a petrol engine.
Human powered.
A child's tricycle is best known, but adult tricycles are becoming more common. The adult trikes will have a chain, gears and are recumbent (the feet are in front of the body). They come in two main styles: tadpole with two wheels up front and one in back and delta with two wheels in the back and one wheel in the front. Almost always the front wheel or wheels steer the bike, and power goes to the back wheel or wheels.
Some trikes are "fully faired" (covered in a shell to cut wind resistance). These are called velomobiles.
Other trikes are built to carry cargo or passengers (also called a "cycle rickshaw" or "pedicabs").
Motor driven.
Motorcycles also come in three wheeled versions. Some people like them for better balance or more room.