Broadcast television is the most common form of television in the United States. Broadcast channels use public airwaves to transmit programs that are theoretically available to any TV set within range of a broadcast transmitter, at no cost to the viewer. As such, most broadcast channels – so-called “commercial channels” – gain revenue through advertising. Think CBS, ABC, NBC, or The CW. Non-commercial channels, such as PBS, gain revenue through donations or other means.