There are two common types of heating systems used in a modern home. One is a hydronic (hot water) system and the other is forced hot air. Both systems use fossil fuels to create the heat needed to condition the home, however hot air systems can use electric that is 100% efficient but could be expensive to run. A standard furnace or boiler that is in the 80% efficiency range uses either a masonry or B-vent chimney to vent the appliance. A furnace or boiler with an efficiency rating of 90% generally uses PVC or CPVC piping to the outdoors because this is known as a condensing appliance. A condensing appliance produces condensate (water) and needs to pumped or drained to a place in the home because it could freeze if it goes to the outdoors in the winter.
A hydronics system uses a boiler generally fueled by oil, propane or natural gas. The water is then pumped in piping through the house to baseboard, radiators, radiant floor heat or air handlers. These boilers come with different firing styles; they can be one single firing rate or modulating. Zoning is done by using either circulators or zone valves which are controlled by your thermostats.
A hot air system can also be fueled by the same fuel sources and come with a wide variety of efficiencies. Both style furnaces come with different fan motors. The most common is a PSE (normal) motor and the other is a variable speed motor (ECM). A PSE motor is set by placing the fan speed wires on preset taps. A variable speed motor is set by the technician for the desired performance and then the control board adjusts the fan speed up and down according to the furnace operation and mode. Modern furnaces even come with muti-stage heating and modulating gas valves.
Not as common in the north but are up and coming are heat pumps. Heat pumps can be installed on a normal forced air system and commonly referred to as dual fuel systems. Currently the most common way they are being installed is with ductless air conditioning systems. In the last few years great strides have been made in this field and they are able to work at much colder temperatures than in the past.