Since its introduction in 1985, compact discs have been widely used for a variety of purposes. CD-DA, for digital audio, is by far the most common use. CD-ROM is the general format for computer applications, allowing about 650 Mbytes to be recorded on a long spiral that at normal speed takes an hour to play back, but which can run at higher speed (e.g., double, triple, quadruple) as well as being accessed randomly (requiring around 200 msec per seek).
For video applications, CD-ROM has been problematic. While the MPEG standard is particularly suitable for single speed playback, allowing an hour of compressed video and audio with at least VHS quality to be stored, most movies are longer than an hour. This space limitation has led to investigations of storage schemes to allow at least 2 hours of video to be recorded, which requires over 1 Gbyte of space. Nimbus, with a plant north of Charlottesville VA, developed blue laser technology to make this possible. However, larger companies and consortium opted for even more capacity, on the order of 3 - 7 Gbytes, to allow longer movies, and to allow higher quality (e.g., broadcast or HDTV) through use of MPEG-2 and faster playback speeds (e.g., double speed).
More details can be found in a recent news story.