Short answers, pulled from the story.
An engine, also called a motor, is a machine designed to convert one or more forms of energy into mechanical energy. Energy sources include potential energy, heat, chemical energy, electric potential, and nuclear energy from fission or fusion.
The word engine derives from Old French, from the Latin ingenium. Pre-industrial siege weapons such as catapults, trebuchets, and battering rams were called siege engines, and the word gin, as in cotton gin, is short for engine.
In standard English, motor and engine are interchangeable. In some engineering jargon an engine consumes fuel and changes its chemical composition, while a motor is driven by electricity, air, or hydraulic pressure without changing its energy source, though rocketry still uses the term rocket motor.
The largest internal combustion engine ever built is the Wartsila-Sulzer RTA96-C, a 14-cylinder, 2-stroke turbocharged diesel engine designed to power the Emma Maersk container ship launched in 2006. It has a mass of 2,300 tonnes, produces over 80 MW at 102 rpm, and can use up to 250 tonnes of fuel per day.
Etienne Lenoir made a commercially successful internal combustion engine in 1860. Earlier piston engines were tested in France in 1807 by de Rivaz and the Niepce brothers, and theoretically advanced by Carnot in 1824.
Diesel engines are 40% more fuel efficient than comparable gasoline engines. They produce lower hydrocarbon emissions but greater particulate pollution than gasoline engines.
Exhaust gas from a spark ignition engine is mostly nitrogen at 70 to 75% by volume, with water vapor at 10 to 12% and carbon dioxide at 10 to 13.5%. It also contains carbon monoxide, which is highly toxic, along with hydrogen, oxygen, unburnt hydrocarbons, and trace compounds.