What is the difference between Blu-ray Disc and DVD?

Just as DVD meant a five to 10 times increase in storage capacity compared to CD, Blu-ray Disc represents an increase over DVD capacity by five to 10 times. This is due, among other reasons, to the usage of a blue instead of a red laser and improved lens specifications, allowing for a much smaller focus laser beam which enables the recording of much smaller and higher density pits on the disc.


Due to the fact that the data layer on a Blu-ray Disc is placed much "closer" to the laser lens than in DVD, there is less distortion resulting in significantly improved tolerances. Hence, more precision and ultra-high storage densities are now possible.

Informatin reference from blu-raydisc website