Prof Crackaquack sez:
Blu-ray Disc (aka BD) is a high-density optical disc format for storing digital information, including high-definition video. The name Blu-ray comes from the blue/violet laser beam used to read and write this type of disc. The blue laser's shorter wavelength (405 nm) means that far more data can be stored on BD than on the ordinary DVD format, which uses a red laser with a wavelenght of 650 nm. A single-layer Blu-ray Disc can store 25 gigabytes (GB), more than five times the capacity of a single layer DVD (4.7 GB). Consequently, a dual-layer Blu-ray Disc can store 50 GB, or almost six times the capacity of a dual layer DVD (8.5 GB).
Its competitor HD DVD or High-Definition DVD was designed to be the successor to the standard DVD format and is a logic continuation of it derived from the same underlying technologies. Ironically, it's kind of a Blu Ray disc format too since all variants except the 3x DVD employ a blue laser with a shorter wavelength. It can store about 3 1/2 times as much data per layer as its predecessor (maximum 17 GB per layer instead of 4.7 GB per layer).
So then, there you know it. Warner Bros. Entertainment will be releasing its high-definition titles "exclusively in the Blu-ray disc format beginning later this year." Barry Meyer, Warner's Chairman & CEO, described the move as a "strategic decision focused on the long term and the most direct way to give consumers what they want." I don't know what Barry Meyer looks like, but the CEO of the HD DVD Promotion Group strongly reminds me of a famous socialist I read about. No wonder they used red lasers to begin with.
Hat tip Smetty's Soapbox.