The operation of a thermal power plant is explained in a logical manner with help of animation in this video. Starting from the very basic question a conceptual overview of Rankine cycle is provided here.
source/image(PrtSc): Learn Engineering
Topics such a Generator, Steam turbine, condenser, feed water pump, boiler are illustrated initially. The basic Rankine cycle is modified and use of super hearing, reheating and feed water heating (deaerator) is explained there after.
Thermal power plants use water as working fluid. Nuclear and coal based power plants fall under this category. The way energy from fuel gets transformed into electricity forms the working of a power plant. In a thermal power plant a steam turbine is rotated with help of high pressure and high temperature steam and this rotation is transferred to a generator to produce electricity.
When turbine blades get rotated by high pressure high temperature steam, the steam loses its energy. This in turn will result in a low pressure and low temperature steam at the outlet of the turbine. Here steam is expanded till saturation point is reached.