Rank (Halo 3)
From Halopedia, the Halo wiki
This page lists the ranks that are used in Halo 3's Matchmaking.
The player has both a Global (main) Rank, which is the Rank that is shown in custom games, forge and on the service record, and a separate rank for each individual playlist.
Playlist rank is made up of the EXP the player has gained in that single playlist, while the Global rank is made up of all of the EXP gained in all of the playlists (plus more if the player has had the Gamertag before the TU2 update).
Do note that Global Ranks (and only Global ranks) can be skipped. For example, a player can go straight from Gunnery Sergeant Grade 2 to Lieutenant Grade 1, missing out Gunnery Sergeant Grade 3 if their highest skill and EXP meet the criteria to do so.
Bungie.net tracks the player's rank history, providing information on when they obtained a rank and details any ranks they have skipped.
List of Ranks
The ranks and requirements of Global ranks.
The ranks and requirements of playlist ranks, which will only show up at that Playlist and Bungie.net.