Before we can specify a location, we have to specify a coordinate system. A 3D coordinate system has three axes: the x axis, the y axis, and the z axis. These three axes start from the origin of where the three axes intersect.
The positive x axis starts from the origin and starts moving endlessly in a certain direction, while the negative x axis moves in the opposite direction. The positive y axis starts from the origin and moves in an upward direction at 90 degrees to the x axis, and the negative y axis moves in the opposite direction. This describes a 2D XY plane, which forms the basis of a 2D coordinate system.
The positive z axis starts from the same origin as the x and y axes and is perpendicular to the X and Y axes. The positive z axis can go in either direction of the XY plane in order to form a 3D coordinate system.
Assuming that the positive x axis...
