The "Call of Duty: Modern Warfare 2" Cross-Gen Bundle includes the base game and allows you to play on both current-generation consoles (such as the PlayStation 5 and Xbox Series X/S) and last-generation consoles (such as the PlayStation 4 and Xbox One).
For some dual-generation games, you can purchase both versions at once this is known as a cross-generation bundle. Owning a cross-generation bundle gives you access to both versions of the game.