Add-ons or expansions (also called expansion packs) are content created for games that is released separately from the main game release. Downloadable content (DLC) is a specific form of add-on distributed through the internet.
Fallout: New VegasEdit
Fallout: New Vegas also features add-ons, with a current total of four pre-order bonuses and six add-on packs.
Fallout 4 will also feature add-ons, the exact count and contents yet to be revealed. However a Season-Pass can be already purchased which will grant access to all add-ons released troughout Fallout 4's lifecycle.