In real life, we can tell where objects are by measuring distance between them. As for placing them, moving them, and keeping track of where they are nature has developed a pretty good system. On the computer though, we have to somehow keep track of objects in a 3D scene. Mathematicians have developed the coordinate system. You have probably learned in geometry about the X and the Y axis. Well, these two axis define a coordinate plane, that is, a two dimentional world. However, to work in three dimentions, we need one more axis, the Z axis
