MP3 is a file format of audio files.
We use the mp3 mediawiki template to reproduce them on this web:
# ''Toccata E Fuga'', [[Bach]]
#: {{mp3|Fpl-favsong-1}}
The .mp3 may be left out, since the template puts it back; {{mp3|Fpl-favsong-1.mp3}} works just as well. A second argument names the track, for the tooltip, for a screen reader, and for what gets printed on paper — otherwise the file name serves for all three. A file that is not on the wiki says so in red instead of becoming a player that cannot play.
Nothing is downloaded until you press play, and only one player sounds at a time, which is what makes a page such as Elena's songs — seventy-odd recordings on one page — reasonable to open at all. The drawing lives in MediaWiki:Gadget-mp3-styles.css and the behaviour in MediaWiki:Gadget-mp3.js; the markup they work on comes from Widget:Mp3.
The older {{Audio|name=Fpl-favsong-1.mp3}} still works and now calls this same template. What it used to do, and why it had to stop, is in Blog:Hacks/mp3 files in mediawiki without flash.