The answer to 'difference between water heater and' is that a water heater and a furnace are two different types of home heating systems that serve different purposes. A water heater is used to heat and store hot water for use in sinks, showers, and appliances, while a furnace is used to heat the air in a home and distribute it through ductwork.
Water heaters come in electric, gas, and tankless varieties, and are typically located in a basement, garage, or utility closet. Furnaces can be gas, electric, or oil-fired, and are usually installed in a basement, attic, or closet. Water heaters have a tank that stores hot water, while furnaces use a heat exchanger to warm air that is then blown through the home's ductwork.