In [b]3 dimensional geometry[/b], a coordinate system refers to the process of identifying the position or location of a point in the coordinate plane.[br][br]Three lines perpendicular to each other pass through a common point, it is called the origin, and the 3 lines are the axes: x-axis, y-axis, and z-axis, respectively. O is the observer, and with respect to its position, any other point is measured. The position or coordinates of any point in 3D space is measured by how much it has moved along the x, y, and z-axis, respectively. So, if a point has a position (3, -4, 5), it means that it has moved 3 units along the positive x-axis, 4 units along the negative y-axis, and 5 units along the positive z-axis.[br][br]