A diagram of a cylinder used in four-stroke gasoline engines:
C – Crankshaft
E – exhaust camshaft
I – inlet camshaft
P – piston
R – connecting rod
S – spark plug
V – valves, red: exhaust, blue: intake.
W – cooling water jacket
gray structure – engine block.
An Internal Combustion Engine (commonly abbreviated as "ICE") is a device to generate heat, via the combustion of a combination of fuel and an an oxidizer, triggered by a spark plug. The force resulting from the expansion of the combusted gasses applies direct force to a component of the engine, normally a piston, which in turn pushes a crankshaft. Each combustion chamber/piston combination is referred to as a cylinder, and multiple cylinders are used to generate maximum power and efficiency in a smooth manner.
While designs for ICEs had been patented as early as 1807, the first successful internal combustion engine was built by Étienne Lenoir in 1858-59, and the first working version of the modern of an ICE was developed by Nikolaus Otto in 1876. Otto was also the inventor of the four-stroke cycle, described as intake, compression, combustion (or power), and exhaust.