There are three concentric walls: Wall Maria, Wall Rose, and Wall Sina, which protect humanity from giant humanoid creatures called Titans.

The Survey Corps is a military branch dedicated to exploring the world outside the Walls and combating the Titans.

ODM gear, or Omni-Directional Mobility gear, is a piece of equipment used by the military to maneuver in three dimensions, allowing them to fly through the air during combat with Titans.