For instance, when you create a Cube object with the 3D Cursor at the

origin of your scene, which has a zero value for all 3D axis, you will have

the Cube placed at the exact center of your scene (Figure 2.17).

Figure 2.17 - Cube at exact center

Since the origin point for the Cube is in the middle of the object, you

have an object with the bottom half below the "ground plane" if you

consider that your Z-axis zero level is the ground or floor for your scene

(Figure 2.18).