A Pressurized Water Reactor (PWR) is a type of nuclear reactor that uses water as both a coolant and a neutron moderator. In a PWR, water is kept under high pressure to prevent it from boiling, even at high temperatures. This pressurized water circulates through the reactor core, where it absorbs heat generated from nuclear fission of fuel, typically uranium. The heated water then flows to a steam generator, where it transfers its heat to a secondary water system, producing steam. This steam drives turbines to generate electricity. PWRs are widely used in commercial nuclear power plants due to their safety features and efficiency.