The answer to 'what is water heater' is a household appliance that heats and stores water for domestic use. Water heaters come in a variety of types, including electric, gas, tankless, and solar-powered models, and are an essential component of a home's plumbing and hot water system.
Water heaters work by heating water and storing it in a tank, so it's ready for use when needed. The water is typically heated using electricity, natural gas, propane, or even solar energy. Water heaters come in a range of sizes, from small units for apartments to larger models for larger households, and their efficiency and energy usage can vary significantly based on the type and size.