A furnace is an appliance used to generate heat for all or part of a building). It is a major component of a central heating system and is permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water). The most common fuel source for modern furnaces in North America and much of Europe is natural gas). A furnace transfers heat to the living space of the building through an intermediary distribution system. If the distribution is through hot water or through steam, then the furnace is more commonly called a boiler).
The terms "heater," "furnace," and "boiler" are often used interchangeably, but they are separate components that collectively warm your home. A furnace is essentially what creates the heat in your home or building and is responsible for pumping warm air into different rooms. Without a furnace, even if you were to turn the heat on, it would not be able to produce warm air. A heater is a broad term used to describe a wide array of devices that produce and emanate heat, including space heaters, boilers, fire, hand-warmers, and electric blankets.
Furnaces get their name from the Greek word "fornax," which means oven. The first furnaces were stone or clay structures that used coal and/or wood to create intense heat. These furnaces were primarily used for ceramic work, such as with kilns, and smelting ore to create metal objects, tools, and materials. Modern-day home furnaces tend to run off gas or electricity and are much safer and contained than their older counterparts.
