Why are portable media players also called mp3 players?

Portable media players are often referred to as MP3 players because MP3 is one of the most popular audio file formats used for storing music and audio content. While these devices can support various formats, the term "MP3 player" became synonymous with portable media players due to the widespread adoption of the MP3 format for music playback. This nomenclature reflects the primary function of the devices, which is to play digital audio files.