The answer to 'what is water heater' is a household appliance that heats and stores water for domestic use. Water heaters are essential for providing hot water for showers, laundry, dishwashing, and other household needs. They come in a variety of types, including electric, gas, tankless, and solar-powered models, and can be installed in the basement, garage, or closet of a home.
Water heaters typically have a storage tank that holds 30-80 gallons of water and maintains it at a set temperature, usually around 120°F. The tank is insulated to minimize heat loss and keep the water hot until it's needed. When hot water is used, the tank is automatically refilled and reheated to maintain the desired temperature.