Central heating and air conditioning systems come in many different types. The right one for you will depend on where your property is located, i.e. what kind of weather conditions you get, the size of your home and your own personal needs, i.e., your family size. The idea behind any system is the same, i.e. when it’s cold you want to heat the house, and cool it when it’s warm. That will either involve moving air or moving water. All the systems work on either one of these principles or a combination.heating and AC has some nice tips on this.
Presumably the most common central heating system in the US today is a gas-forced air system. Basically a furnace heats up the air which is then blown up by a fan system through your home. If you choose to cool the house, i.e. in heat, the same machine takes the house inside your home and moves it into a refrigerator. That’s the most basic explanation, but these systems don’t really have a lot more. Are they working? Yes, but they are not very efficient, prone to drafting, and can lead to bills that are unnecessarily high. You could have a standalone electrical system that is popular because installation is cheap. But running is expensive and you can’t add air conditioning to the same system so if you need cool air in the summer, that’s an additional cost.
Often referred to as Hydronic you could have a water-based system. A hot water system works on the basis that water is heated and distributed throughout your home through a system of radiators that then emit heat into those individual rooms. Radiators in the 1960s have been smaller and more effective than those in operation but it is also not an extremely powerful device and can not be used for air conditioning.