World space is the universal coordinate system used to track objects in the scene. When you look at the home grid in the viewports, you see the world-space coordinate system. World space is constant and immovable. By convention, world-space coordinates are always expressed as XYZ coordinates, as opposed to the UVW coordinates of object space.

All objects in your scene are located in world space by their position, rotation, and scale (their transforms).

Some modifiers operate in world space. See World-Space Modifiers (WSMs).