These numbers probably sound like gibberish unless you're a techie, so here's a real-world example of a Blu-ray disc's capacity. A DVD can hold about four hours of standard definition video, while a Blu-ray disc can hold more than 20 hours. That's impressive because a single Blu-ray disc could hold an entire season of some television shows, eliminating the need for massive boxed sets.
The real attraction of Blu-ray discs, however, is their ability to store better-quality, high-definition video. Standard DVDs just don't have the capacity to carry feature-length movies in high-definition, but one dual-layer Blu-ray can hold about nine hours of high-definition content.
All of this is important to television fans because Blu-ray discs allow you to get the most out of today's high-end TV sets. No matter how good your DVD player is, it won't deliver a picture as good as those available from top-quality Blu-ray players showing a Blu-ray disc.