Outside of it being the main campaign for Destiny 2, we don’t know much about the Red War campaign. Presumably, this is the story that will have Guardians regain their powers, fight back against the leader of the Cabal, Dominus Ghaul — and reclaim their home.
The Red War contains many story missions, according to the Destiny 2 gameplay reveal event. However, Destiny 2’s campaign will also feature Adventures. Adventures are essentially side missions that Bungie designed to fill out the world. During the reveal event, Steve Cotton, Destiny 2’s world lead, described Adventures as anything from treasure maps to dungeon-like caves with the promise of loot.
Adventures will be marked on your map (a new feature in Destiny 2) by new non-playable characters scattered around the worlds. These Adventures will support the Red War campaign's story missions to make the world seem more alive.
If Bungie holds to the same design philosophies as Destiny, the Red War campaign will end at the raid, with big baddy Dominus Ghaul presumably holding the title of final boss. Bungie will reveal more information on the raid and the Red War campaign closer to Destiny 2’s launch on Sept. 8.