Downloadable Content, or DLC, was content that the player can choose to buy in addition to the game to add more to it.
Harvest Moon: Skytree Village had four differen DLC packs, though only two of them are paid DLC and the other two are simply optional free addons.
NOTE: As of the Nintendo Eshop's closure on March 27th, 2023 this DLC in unobtainable through legitimate means. Players who had previously downloaded it can still access it on their device, but no new players can download it.