Halo 5: Guardians releases around the world today and tomorrow here are some useful links to help you to get to know the game.
The Competitive Skill Rating
Halo 5: Guardians Launch Playlist Details
Halo 5: Guardians Forge
Halo 5: Guardians new Requisition (REQ) System
Halo 5: Guardians Achievement list
Spartan Companies
Commendations and Medals list