MP3, short for MPEG-1/MPEG-2 Layer 3, is a format for storing digital audio. It uses an advanced type of audio compression, which reduces the file size with little reduction in audio quality. mp3 is used in software applications, digital audio players, home stereo devices and music distribution over the Internet, but is also used for other purposes such as real-time digital audio transmissions over ISDN.

An mp3 file (or simply an mp3) is a file that contains mp3-compressed audio data. It is played using an mp3 player. You can recognize mp3 files by their file-extension (the end of the filename), which is .mp3.

The mp3 format, (MPEG-1/MPEG-2 Layer 3) has been an ISO standard since 1993. Unlike other digital music formats, mp3 is backward and forward compatible ensuring that every mp3-file created in the past can be played on all current and future digital audio players. Reciprocally, old software and hardware devices can play an mp3 file created with the most recent software. As illustrated by the "mp3 - playing everywhere" initiative, consumers can be assured that their current investment in creating an mp3 content library will never be obsolete.