Now I've got to buy the White Album again...or at least Star Wars.
Normal optical drives use red lasers. The new optical drives using "Blu-Ray" lasers take advantage of their shorter wavelength to pack a lot more data into the same space on a disk.
One result: a 3 cm optical disk that can hold 1 Gigabyte.
Another result: DVDs that can hold 27 Gigbytes, which is 13 hours of normal TV, or, the Holy Grail, 2 hours of HDTV. This latter is the killer app that will suddenly make HDTV worth the bucks when you can see prerecorded movies at that resolution. I see HDTV DVDs coming out in about three years or less.