Question: what is the difference between hd dvd and dvd?
Answer: The major difference between Blu-ray/HD DVD and DVDs is capacity -- that is, both Blu-ray and HD DVD can store more information than current DVDs on the same size 12cm optical disc we're all used to. ... In contrast, HD DVDs can store up to 15GB on a single layer while Blu-ray can hold 25GB on one layer.