Commercial television is profit based and generates its earnings by airing commercials for various products. Advertisers, ranging from auto makers to food and beverage companies, pay thousands of dollars--sometimes millions, particularly during programs with a very large audience such as the Superbowl--for 30 seconds of airtime.
Public television stations do not air commercials, so therefore the programming is for the most part uninterrupted. As a non-profit entity, public television stations are funded by membership, donations and the government. According to PBS, more than 61 million people tune in to public television during an average week.
The largest networks in the United States--known as the "big three" are ABC, CBS and NBC. All major networks can be accessed by television regardless of whether or not you have cable.
The most well-known public television network is PBS, which distributes programming to 356 member stations nationwide.
Both commercial and public television came about in the United States during the 1940s and subsequently grew in viewership. The most popular early shows included the "Howdy Doody Show," the "Perry Como Show" and "Texaco Star Theater."
"Howdy Doody" was the first children's program aired on commercial television. It was also the first show to be aired in color, a milestone that occurred in 1955.