An MP3 tag is a metadata container in an MP3 file (ID3). It tells the information about the mp3 file and embedded in the file structure and contains data for tags like artist, track number, album, genre, year, etc. This information can be used by MP3 players, media players, software players, and can also be edited using MP3 tag editors.
When you're playing a song and see the album art image, name of the artist, album name, etc, all of these information contained in ID3. There are two unrelated versions of ID3:
ID3V1: The older ID3v1 tag which is located at the end of an MP3 file takes up 128 bytes of space. This metadata container supports up to 30 bytes for tags such as artist, album, etc.; shorter tags such as genre have a 1 byte allocation. The updated ID3v1.1 tag has an additional track number tag that the original ID3V1 doesn't.
ID3V2:The ID3V2 specification which was released in 1998, is a frame-based container that is located at the beginning of an MP3 file. So far, there have been 3 revisions of this specification (ID3V2.2 / ID3V2.3 / ID3V2.4). Compared to the old ID3V1 and ID3V1.1, this format is very flexible and can contain up to 256Mb of metadata (max. 16Mb per frame). Currently there are 84 different frame types - you can use some of these to embed album art, lyrics, Website addresses, and more.
