“A .wav file (pronounced ‘wave’) is the file an artist sends to a digital distributor for music. A .wav file allows for all of the sounds that have been produced in a track to be able to be heard when someone downloads it. The .wav file is what is played when you press the preview button for a song on iTunes. The .wav file is then compressed into an mp3 file for the buyer.
The fact that BTS tweeted a photo of a downloaded .wav file may indicate a possible release of a song or track. As I stated earlier, the .wav file is sent to a digital distributor (CDbaby, for instance is the number one distributor in the US music market) and the distributor sends the file to he set up on iTunes, Spotify, virtually any streaming or downloading service for music.
Our boys could possibly be dropping a song/track ☺️” - @minfreakingyoongi