The prototype of the steam turbine is said to have been the Hero's aeolipile made by the Greek mathematician Hero of Alexandria in 120 B.C., which was a sphere with bent pipes attached to its circumference which caused the sphere to spin in reaction to the steam expelled from them.

Much later, in 1629, the Italian architect Giovanni Branca conceived Branca engine that operated on the same principle as today's impulse turbines, but it remained at the conceptual stage and never saw practical use.

More than 150 years after that, at the end of the 19th century, development and practical application of steam turbines finally got underway. In 1882 Carl G.P. de Laval of Sweden developed an impulse turbine, and in 1884 Charles Parsons of England developed a multi-stage reaction turbine that was put to practical use in 1889 for electrical power generation. In 1895 Charles Gordon Curtis of the United States developed a two-stage multi-speed impulse turbine, and in 1898 Auguste Rateau of France developed the first practical version of the type of turbines still in use today.

A steam turbine is a device that converts the thermal energy of steam into mechanical energy by using it to turn the blades of a rotor. High-temperature, high-pressure steam passes through a nozzle or fixed blades and spurts out and expands, or has its direction altered into a high-speed jet that is directed against rotor blades which spin the shaft to which they are attached, creating rotational energy. In simple terms, the steam turbine's rotors are turned by the force of the steam in just the same way that a waterwheel is turned by the force of the flowing water.

Steam turbines used in electric power plants, factories, etc. use boilers burning fossil fuels such as coal, fuel oil, or natural gas, or alternative fuels such as biomass, refuse, or other waste materials, in order to produce large quantities of superheated, high-pressure steam. This steam is channeled into the turbine, where it is ejected from nozzles. At that instant, the depressurization (expansion) of the steam creates a high-speed flow (pressure is converted to velocity: Bernoulli's theorem). This jet of steam is then directed against the turbine blades, causing them to revolve (velocity is converted to kinetic energy).

Depending upon the behavior of the steam in the vicinity of the blades, steam turbines are divided into two major classes: impulse turbines and reaction turbines.

In impulse turbines, high-velocity steam from fixed nozzles impacts the blades, and this impulse drives the blades forward, causing the rotor to turn.

The main feature of these turbines is that the heat drop per stage can be quite large, allowing for large blades and a smaller number of stages.

In reaction turbines, high-velocity steam from nozzles striking blades also produces impulse, but the steam jet runs into the blades and the main force turning the rotor is the reactive force produced by the expansion of steam flowing off the rotor blades themselves.

The main feature of this type of turbine is that in contrast to the impulse turbine, the heat drop per stage is lessened, so the blades become smaller and the number of stages increases.

Further subclassification of turbines is possible based upon the number of rotor stages, steam extraction, direction of vapor flow, and so forth.

The electricity essential to our daily lives is produced at power plants, and it is steam turbines that are the prime movers driving the generators at both thermal and nuclear power plants.
Steam turbines are also widely used as drivers for large ships, while smaller steam turbines are used to drive pumps and fans at petrochemical plants.
Thus, while we may not see them every day, steam turbines are intimately related to our daily lives in many ways.

The main components of the thermal and nuclear power plants essential to our daily lives and to industry consist of a burner (or nuclear reactor), boiler, steam turbine, and generator.
Thermal power plants use the combustion of fossil fuels such as coal, oil, or natural gas, and nuclear power plants use a nuclear reaction to heat their boilers and produce steam, which is used to drive the turbines, which in turn drive the generators which produce the electricity.

Biomass power generation is a type of thermal power generation in which agricultural waste byproducts such as bagasse (the residue of sugar-cane stalks after they have been crushed to extract their juice) are used as fuel. Many such plants have been established in countries in warmer regions of the world where crops are harvested year-round.
Biomass has attracted considerable attention as a method of power generation that does not increase the amount of CO₂ in the atmosphere, an important consideration now that prevention of global warming has become such a concern. (When burned, it releases into the atmosphere only the amount of CO₂ that the plants composing it absorbed out of the atmosphere in the first place.)
Power generation from waste incineration is also another form of thermal power generation, involving the construction of waste incineration plants in a way that enables capture of the surplus heat energy to produce electricity. Garbage is the main form of fuel, but in some cases sludge from sewage treatment plants is also used. Like biomass, power generation from incineration of waste does not produce a net increase in CO₂, so it is an environmentally friendly source of power.

If the pipes of a petrochemical plant are its arteries, then its heart is a pump. Yet unlike the blood in the human body, the liquids flowing through a petrochemical plant tend to be both volatile and flammable, so that even a minor leak can cause a major explosion if exposed to flame. That is why open flames of any kind are prohibited in such plants and their vicinity.
In such an environment, there is also the danger that a spark from a motor could be a source of explosion. Steam turbines, which use no electricity, are free from the risk of igniting an explosion, and are therefore used as the motive force driving the pumps and fans in such plants.

There are various types of drivers used on ships: diesel engines (slow, medium, or high speed and size), turbines (gas, steam), and others such as nuclear power, jet propulsion, etc.
Steam turbines are used for comparatively large high-speed commercial and naval vessels