From Press Release:
Fight. Collect. Bank. Invade.
Gambit is an all-new hybrid game mode for Destiny 2: Forsaken.
Gambit is a 4v4 hybrid mode that merges PvE and PvP experiences into an epic battle. It’s a new way to play Destiny 2, offering something for all players to enjoy, appealing to those who thrive on the competition and unpredictable elements of PvP gameplay, while seamlessly blending the collaborative and cooperative elements of PvE.