ID3 tags are where metadata with most MP3 files is stored. It isn't really a standard because different people/companies made contributions, but because of its wide use almost every program that plays or creates MP3 files can read this metadata. There is so much information you can put in these files but almost noone uses most of the fields. You can embedd album covers, booklet pages, titles, artists, genre, ISRC, UPC, website links, and the list goes on. Oh...
