Spatial describes how objects fit together in space, either among the planets or down here on earth. There's a spatial relationship between Mars and Venus, as well as between the rose bushes in the backyard.
Spatial has to do with the distance between things, so mathematicians and computer scientists love using the word. "They measured the spatial relations of ping-pong balls in the gravity-free room." It can also refer to how people perceive the objects in front of them. If you're not wearing your glasses, your spatial perception might be off. If you're a space cadet, you might wander off into space. Not surprisingly, spatial is from the Latin word spatium for "space."