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, allowing it to absorb heat generated from nuclear fission in the reactor core. This heated water is then circulated to a steam generator, where it transfers heat to a secondary water system, producing steam to drive turbines for electricity generation. PWRs are the most common type of nuclear reactors worldwide, with many located in countries like the United States and France. They are designed with multiple safety systems to prevent overheating and contain radioactive materials, making them a crucial part of the global energy landscape.