There are three types of podcast, audio, video and enhanced. The audio podcast is a speech only file, presented in an MP3 format. The majority of recorded lectures currently utilise this format. The video podcast is a full motion video file usually presented in a MPEG or MP4 format. There are few limits to what can be included in a video podcast, anything you see on television can be utilised in this format with the appropriate technical know how. The enhanced podcast is a speech only file but with the inclusion of more interactive elements such as images, hyperlinks and chapterisation. These files are presented in an .m4a format and can be viewed using iTunes on both PC and Apple platforms. The enhanced podcast is not as common as its audio and video counterparts largely because the authoring of such files is currently, almost exclusively an Apple based activity. Although it is possible to add identical elements to an audio file in Windows, this is far from a simple process involving changing security settings within windows media player, and as a result those authoring podcasts on a PC have generally steered clear of the enhanced file type.