What is Blu-ray Disc?

Blu-ray, also known as Blu-ray Disc (BD), is the name of a next-generation optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of the world's leading consumer electronics, personal computer and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson). The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data. The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codecs will offer consumers an unprecedented HD experience.

While current optical disc technologies such as DVD, DVD±R, DVD±RW, and DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser instead, hence the name Blu-ray. Despite the different type of lasers used, Blu-ray products can easily be made backwards compatible with CDs and DVDs through the use of a BD/DVD/CD compatible optical pickup unit. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision. This allows data to be packed more tightly and stored in less space, so it's possible to fit more data on the disc even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB.

Source: Blu-ray.com

What you think? ive heard of this when ive watched "Pirate of the Carribean: World's End",

you know at the end of movie trailer before the movie itself, it says, available now on DVD and Blu-ray Disc, that's why i was confused what is blu-ray disc. does this mean DVD was going to out?

I guess not cause Blu-ray Disc still cost much and you have to buy the player also.
While DVD are very affordable, but of course the video quality is not as good as the Blu-ray.

too expensive, will settle for dvd

i have many blue ray disk.
its good because the quality of the video is clearer.
although it cost more than dvd's, if you want to watch your videos in high HD style, blue rays are pretty good(=