Most homes in the area keep warm by using forced air furnaces, which heat the air in a single location and then distribute it throughout the house via a series of ducts. Furnaces are dependable and inexpensive to operate, which is one of the reasons why they see so much use. But they also run into problems from time to time, like any system does, and when that happens you need a trained technician to perform repairs.
We often pride ourselves on self-sufficiency around here, and many homeowners like to conduct little do-it-yourself repairs around their homes. In cases involving your furnace, this is a big mistake. Heating systems are complicated and delicate, and most involve potentially dangerous components such as gas lines and flame burners. That means that you need training and licensing even to perform a diagnosis, much less repairs.