An engine is basically a mechanical machine that takes an energy source to produce some sort of output, normally in the form of movement. There is an infinite number of engine types that power all sorts of machines; however, since the site is game oriented this articles attention will be placed towards internal combustion engines, which are the most common ones used mainly to power all sorts of vehicles. An internal combustion engine, as the name suggests, burns it´s energy source (normally fuel) in combination with air inside a combustion chamber to crate an expansion of gases, which are converted to mechanical movement.
Engines like jet engines and turbines, although do not have an intermittent cycle of combustion are also considered ICE´s because the burning of fuel is also done within an internal combustion chamber.
In the automotive world, there are two main types of engine. The conventional design uses pistons, in a V or linear layout in most cases to convert the energy stored within the fuel to movement. Another, more unusual type is the Wankel engine, mainly manufactured nowadays by Mazda, which uses a triangular shaped piston to generate rotary motion inside a circular chamber.
The energetic problem has forced engineers to search for new types of engines that rely on something different than fossil fuels, however, very few of this type of engines have appeared in gaming, being the most popular electric cars.