MP3

MP3 (formally MPEG-1 Audio Layer 3) is a digital audio compression algorithm that achieves a compression factor of about 10-to-1 while preserving reasonable sound quality. It does this by optimizing the compression according to the range of sound that people can actually hear. The MP3 specification was published in August 1993 as what then became the most powerful algorithm in a series of audio encoding standards developed for MPEG-1 under the sponsorship of the Moving Picture Experts Group (MPEG) and formalized by the International Organization for Standardization (ISO).

Description
MP3 is very different from Layer 2 (filename extension .mp2), using an additional (MDCT) layer to increase frequency resolution. Its scale factor groups are more optimized for the human ear, and it uses nonlinear and.

MP3 files (filename extension .mp3) can be downloaded from the web and can be played using software available for most operating systems, such as for Windows, MacAmp or iTunes for Mac, and  for Unix.

MP3 files are usually downloaded completely before playing but streaming MP3 is also possible. A program called a "ripper" can be used to copy a selection from a music CD onto a hard disk and another program called an encoder can convert it to an MP3 file.

Support by Apple
Apple Computer first added formal support for the playback of MP3 content with the release of QuickTime 4.0 in June 1999. MP3 is supported for music playback on iPads, iPods, and iPhones from Apple, though AAC has become more accepted due to its improved compression ratio to audio quality.