PCM = Pulse Code Modulation; if I understand correctly, it's the technical designation for how audio is encoded as the kind of ROM samples that synths such as the XP then "play back," which is why such synths are called "sample playback" synths. In the older series (JV80/880/90/1000) and the JV1080/2080, the optional "PCM Card" contains waveforms you can use to form new patches (the cards also contained patches).

I have the video and have learned a great deal from it, including a lot of tips that are in the manual but don't seem as useful at first as they are in the video (like navigating around the keyboard). It's most useful if your video player and keyboard are together so you can hit pause and perform the functions on your own XP the dude in the video is performing on his.