Broadcasting is the distribution of video and audio content to a whole audience via any audio or visual mass communications medium, but generally one using electromagnetic radiation. The receiving parties may add the relatively large subset or a general public thereof. Broadcasting has been needed for purposes of non-commercial exchange of messages, private recreation, experimentation, emergency communication, and self-training such as amateur (ham) radio and amateur television (ATV) in addition to commercial purposes like popular TV stations or radio with advertisements.