How to record high-definition video
Right now, there are only two ways to record high-def in its true, high-resolution glory. You can use either a HDTV DVR, such as DirecTV's HD TiVo, or a D-VHS deck. It's impossible to record high-def video on a standard DVD recorder or VCR, although you can record a lower-resolution version of an HDTV program that looks pretty good.
An HDTV DVR is the most versatile and most common way people record HDTV in full resolution. Most HDTV DVRs are built into satellite tuners and cable boxes, but a few are also available for over-the-air HDTV broadcasts.
An HDTV DVR allows you to schedule recordings, as well as pause, rewind, and fast-forward live TV, just like TiVo but with a sharper picture. There's no easy way to archive or save HD DVR recordings in high-def, although you can record lower-resolution versions to DVD or even VHS.
You can also get a special kind of VCR, called a D-VHS deck, to record high-def onto videocassette. These tapes make it easy to archive HD video, but like any tape, they can wear out, and they require manual fast-forward and rewinding. D-VHS decks are also notoriously finicky about what inputs they'll accept: they usually only accept HDTV over a FireWire connection, which most external satellite and cable HD receivers lack. Most D-VHS recordings are made from high-end HDTVs that have FireWire ports. Understandably, these expensive and limited D-VHS decks aren't very popular.
Finally, you can also record lower-resolution versions of HDTV shows, provided that your HDTV receiver or DVR has an S-Video or composite-video output. This downconverted material will still look pretty good, but it won't be HDTV.