Destiny 2 Shadowkeep

They are not giving Forsaken away, Only Destiny 2, Curse of Osiris, And Warmind. You have to still pay for Forsaken.

First, here's a list of existing content that's free to all players:

• All Year 1 story content - including base Destiny 2 campaign and The Red War, Curse of Osiris and Warmind missions
• Access to all Patrol spaces (including Forsaken's Dreaming City and Shadowkeep's Moon)
• Year 1
  Exotics, Nightfall Strikes and Raids, including the
  Leviathan, Eater of Worlds and Spire of Stars
• Year 2
  Exotics
  Thunderlord, Arbalest,
  Outbreak Perfected and
  Bad Juju
• Year 2 matchmade activities Gambit, Gambit Prime, Black Armory, The Menagerie and The Reckoning
• Gambit and Crucible Private matches

Additionally, here's the new Year 3 additions you'll also get free access to with New Light:

• The opening mission of Shadowkeep
• The new Moon patrol space
• Shadowkeep's two new Strikes and three new Crucible maps, two returning from the original Destiny (Widow's Court and Twilight Gap)
• All Crucible updates, maps, new modes and events, such as Iron Banner
• New
  Armor 2.0 and Finisher systems
• Themed seasonal events, such as the Halloween-themed Festival of the Lost and Christmas event The Dawning
• Access to all the 'free' rewards of a Season Pass - this includes Seasonal Artifact access and rewards from the free tier, such as the seasonal armor set and an Exotic weapon

To clarify further, New Light (and owning only Shadowkeep) won't give you access to select Forsaken and some Year 2 Annual Pass content. This includes the campaign, Shattered Throne dungeon, Raids and most Year 2

Exotics, plus the newly added subclasses (though if you buy just Shadowkeep, you do get these subclasses).

:)