What is the difference between CD, DVD, and Blu-ray discs?
In brief, CD (Compact Disc) is primarily used for delivery of music, DVD (Digital Versatile Disc) primarily for standard definition (720×480 in the North America, 720×576 in most of the rest of the world) video, and Blu-ray Disc primarily for high definition (1920×1080) video.

Adding a bit of detail to the above, each of these formats can be used for audio, video, or data (such as VideoCD or DVD Audio), and all come in read-only, write-once, and read/write formats. All of these formats have discs of the same diameter (120mm or 4.7in) and look roughly the same.
Compact Disc was commercially released in early 1983, and holds from 650-700MB per disc. DVD was commercially released in 1996 and holds from 4.7 – 8.7GB in the more common formats. Blu-ray Disc was commercially released in 2006 and holds from 25 – 50GB in the more common formats, with BD-XL supporting up to 128GB.
Almost all DVD players and burners support CD formats, and almost all Blu-ray Disc players and burners support DVD and CD formats.
Blu-ray or Blu-ray Disc (BD) is a digital optical disc data storage format. It was designed to supersede the DVD format, in that it is capable of storing hours of video in high-definition (720p and 1080p) and ultra high-definition resolution (2160p).
