What is the difference between a blu-ray disc and a normal one?

all i know is that blu-ray ones are more expensive . can someone explain why ?

please and thanksWhat is the difference between a blu-ray disc and a normal one?
Regular DVDs are unable to store enough info in order to have a full length movie. Blu-ray is a type of DVD that allows more info to be stored, thus supporting high def.What is the difference between a blu-ray disc and a normal one?
Blu-Ray is currently the best in graphics it is more realistic then life.

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