What is the difference between a DVD and CD?

AnswerData on a CD is written is form of small dots. A laser is used in CD drive to read data from CD. The light reflected because of the dots on the CD is translated to 1's and 0's. The difference between a DVD and CD is that DVD uses a more concentrated laser beam. This allows it to read very very small dots. Because the size of the dots is reduced we can save more data on DVD.

Beyond little microdots, the big difference between DVD's and CD's is storage Capacity. CD's (compact discs) can hold between 640 - 700 MB's (megabytes) of information on a single disc. DVD's (Digital Video Discs) can hold 4.7 GB (gigabytes) of information on a single layer disc, and 8.5 GB on a dual layer disc.

Beyond that, CD's hit the consumer market in 1983, and used a laser to read the media (disc) instead of magnetic technology. The standard amount of audio (time) on a CD with CDA sound files (compact disc audio) was approximately 72 minutes. Today, MP3 music files are about 1/10th the size of CDA audio. *This unofficially works out to 10 MB per minute of audio with CDA, and 1 MB per minute of audio with MP3.*

Beyond all those specifications, there is an old technology called Laser Disc, which was almost the same size as an LP (the big ones) record, but also used laser. Based on the the technology that would bring us CD's, the laser disc provided more data storage than a typical CD due to more surface area to write to. This technology was short-lived vs VHS due to the high cost. Even though the discs themselves were cheaper to produce, the equipment required to play cost significantly more than equivalent VHS players.

In the future, HD DVD and Blue Ray technology will rerevolutionize laser technology. Future High Definition Television programs will be shown in 720p, 1080i or 1080p. These video qualities make watching Television as though it's photographic quality instead of dithered like current 480i. The capacity for HD DVD is about 35 GB's per dual layer disc, and Blue Ray is about 45-50 GB's per disc (unofficial specifications from respective Mfrs.)