I don't understand Work Planes

Imagine having a cube and want to measure the distance between the left side and right side. You probe the 2 planes and you create a distance measurement. If your workplane is Z axis or Y axis the machine can "see the line" connecting this 2 planes and can measure it. If you define the workplane as X is like the machine is viewing the part from the sides and instead of seeing the connecting line, it sees a point and thus it cannot measure it.

Other example... Imagine now that on the left side you want to create a measured circle probing with the joystick. You probe and construct a circle with workplane X selected. The machine will fit the circle on the points on that workplane. If you have the Y or Z workplane selected, it will try to create a circle on these sides (front side or top side accordingly) and will give you a circle with a crazy number of dia and center.

When working with a CAD you don't actually really need to change it for probing matters, only in cases as my first example.

Imagine having a cube and want to measure the distance between the left side and right side. You probe the 2 planes and you create a distance measurement. If your workplane is Z axis or Y axis the machine can "see the line" connecting this 2 planes and can measure it. If you define the workplane as X is like the machine is viewing the part from the sides and instead of seeing the connecting line, it sees a point and thus it cannot measure it.

Other example... Imagine now that on the left side you want to create a measured circle probing with the joystick. You probe and construct a circle with workplane X selected. The machine will fit the circle on the points on that workplane. If you have the Y or Z workplane selected, it will try to create a circle on these sides (front side or top side accordingly) and will give you a circle with a crazy number of dia and center.

When working with a CAD you don't actually really need to change it for probing matters, only in cases as my first example.