Which is basically Call of Duty: The Latest One III or IV or Whatever We're Up To Now without any of that story stuff. Thus giving players access to the ranked multiplayer portion of the game for a reasonable price. That reasonable price? $14.99 USD, and its available to purchase now on Steam.
The Multiplayer Starter Pack gives you access to Public Ranked Multiplayer matches and features including Weapon Paint Shop, Gunsmith, Arena, Freerun, Theater, and the Black Market.
Features NOT included in the Call of Duty: Black Ops III Multiplayer Starter Pack:
- Zombies game mode
- Campaign game mode
- Ability to play in Multiplayer custom games
- Ability to Prestige (your level will be capped at 55 in the Starter Pack)
- Access to mod tools or modded content (once released)
- Access to unranked server browser (once released)
- Ability to Fresh Start your profile
- The ability to access Dead Ops Arcade II and Nightmares mode
So yeah, it's exactly what it says it is. As to how it'll work with additional map packs? Well they'll also probably be released separately. As map packs! It's right there in the name.