Look for the Zombies map, the Nuk3town multiplayer map, and various personalization packs (camos and calling cards). System Requirements for BO3 PC
The "real" story is revealed in fast-scrolling text at the start of missions. Your character (the Player) is actually mortally wounded during the first mission in Ethiopia. The rest of the campaign is a simulation occurring within the Player's mind during their final moments, mixed with the memories of John Taylor.
Assuming you have found a valid (e.g., FitGirl’s 64GB version), follow this guide:
: The futuristic single-player campaign and core multiplayer modes.