AM radio today is generally talk radio. In the beginning, AM radio was given permission by the FCC, to operate in America, in order to give the public a source of information and entertainment. AM radio does not have the broadcast quality of FM, since they both operate on two entirely different radio frequencies. The AM radio waves are effected by the sun, so that when the sun went down, an AM stations waves would stretch further across America. There were just a few stations with enough transmitting power to reach a large portion of America’s population. These were powerhouse stations with 50,000 watts of transmitting power. This was enabled, so the people in secluded areas of America would have access to information, that other people were receiving. WSM and WLS were two of the leading powerhouse stations, in the early 1900s.
FM radio was originally formulated, by the FCC, in order to provide “mostly elevator music” to the public. FM radio waves are much closer together, allowing a much better quality sound of music. FM radio is not effected by the sun, thus what you hear in the daytime is the same station at night. It takes much more transmitting power to operate on the FM frequency, compared to AM. FM was soon discovered to be a media frequency that could be used for a profit from the private sector. Elevator music was mostly forgotten and today FMs format includes anything from country to oldies music and many commercials.
I have always said that television is radio with pictures added.