A water heater is a device that heats water for various domestic purposes, such as bathing, cooking, and cleaning. There are different types of water heaters, including tankless, storage, and solar models. They work by using energy sources like electricity, gas, or solar power to raise the temperature of water. Most water heaters have a thermostat that regulates the water temperature, ensuring it stays at a set level. Regular maintenance is important for efficiency and longevity, which may include flushing the tank to remove sediment buildup. Proper installation and safety measures are essential to prevent issues like leaks or overheating.