The term ‘podcast’ is a combination of the words 'broadcast' and 'iPod'. When podcasts first emerged on the scene, it was common practice to store and listen to the audio files on your iPod (or other MP3 player). Since then the name for this format has well and truly established itself, even though the format can, in principle, be used with almost any kind of device - not only with the iPod. Today podcasts can be heard on both computers and smartphones - either by streaming or downloading.
Although radio and television broadcasters are increasingly making their content available online as podcasts, the format is still mainly used by private individuals to share a wide variety of content. Regardless of what interests you have, you should have no problem at all finding a podcast to match.
In the past, podcasts were seen as being audio 'diaries' but nowadays video podcasts (also known as 'vodcasts' or 'vidcasts') also fall under this umbrella term. The principle is the same as with audio podcasts, except that the audio content is also supplemented with visual elements. However, in contrast to audio podcasts, the video podcasts require the full attention of the audience member. One downside of this is that it makes podcasting on the go quite a bit more difficult.