Campaign

Normally referred to as a "Single Player" game, the campaign mode of Halo: Combat Evolved and Halo 2 would not accurately fill this description as it has a Co-op feature that allows two players to play the game simultaneously.

Campaign mode is where all canon from the games comes from. It is the place where the player undertakes the story of the game, meets all Characters, and fights computer-controlled enemies.

The other game mode of the Halo games is Multiplayer where there is no story line and the player plays against other humans.

Halo: Combat Evolved Campaign Levels

 * 1) Pillar of Autumn
 * 2) Halo
 * 3) Truth and Reconciliation
 * 4) The Silent Cartographer
 * 5) Assault on the Control Room
 * 6) 343 Guilty Spark
 * 7) The Library
 * 8) Two Betrayals
 * 9) Keyes
 * 10) The Maw

Halo 2 Campaign Levels

 * 1) The Heretic
 * 2) The Armory
 * 3) Cairo Station
 * 4) Outskirts
 * 5) Metropolis
 * 6) The Arbiter
 * 7) The Oracle
 * 8) Delta Halo
 * 9) Regret
 * 10) Sacred Icon
 * 11) Quarantine Zone
 * 12) Gravemind
 * 13) Uprising
 * 14) High Charity
 * 15) The Great Journey

Halo 3 Campaign Levels

 * 1) Sierra 117
 * 2) Holdout
 * 3) The Road
 * 4) Assault
 * 5) Cleansing
 * 6) Refuge
 * 7) Last Stand
 * 8) The Key
 * 9) Return

Note: Except for the first stage, these names are taken from the list of Halo 3 Achievements. However, the first stage is officially known as "Sierra 117," in contrast with the "Landfall" designation in the Achievements list. Therefore, it stands to reason that the remaining levels will have different titles than their Achievements as well.