Thread:FallenAngelII/@comment-29512888-20180928123907/@comment-1465604-20181002051224

You go into the game files to find data, usually data that isn't usually available in-game. Like if you go into the Just Dance 2015 files, you'll find that the coach is separate from the background video for certain routines, like "Bad Romance (Extreme)" and all mash-ups. The background is just a solid colour, like green.

Or if you go into the files for Just Dance 2017, you'll find the preview video for the beta for "Titanium (Alt)". Sometimes, data mining requires more work, like looking through the files that govern how the games work to figure out things such as how fast a certain move in a fighting game is or hidden text in Zelda games that were never used.

Data mining just means looking at the files for a game, application, etc. to figure things out.