What does the steam engine do?

A steam engine is a heat engine that performs mechanical work using steam as its working fluid. In simple terms, the steam engine uses the expansion principle of chemistry, where heat applied to water transforms the water to steam. and then pushes a piston (cylinder). read more

Steam engines were the first engine type to see widespread use. They were first invented by Thomas Newcomen in 1705, and James Watt (who we remember each time we talk about "60-watt light bulbs" and the such) made big improvements to steam engines in 1769. read more

A steam engine is so inefficient because the fire that burns the coal is totally separate (and often some distance from) the cylinder that turns the heat energy in the steam into mechanical energy that powers the machine. read more