X refers to the left and right direction, Y refers to the front and back direction, Z refers to the up and down direction, and the three axes of X, Y and Z are perpendicular to each other, similar to an angle. You can draw a horizontal straight line as the X axis first, draw the Z axis 90 degrees counterclockwise, and continue to turn 135 degrees as the Y axis.

A coordinate axis is a set of straight lines or lines used to define a coordinate system, and the position of a point located on the coordinate axis is uniquely determined by a coordinate value. In plane analytic geometry, two intersecting lines used as reference lines are the intersection lines of three reference coordinate planes in three-dimensional analytic geometry.