Axis
It can be called a constant or fixed value. If it is not a value but a cell reference then it can be called an absolute reference.
It is a fixed reference point whose elevation above a given datum line
An axis can be defined as an imaginary line about which a body rotates, In math it can be defined as a fixed reference line for the measurement of coordinates.
An absolute reference. An absolute cell reference.
it is a satilite that orbits the moon but im not sure what it is used for .
No, they are called absolute references.
Axis
It is because many things are measured with reference to a fixed point: it space or time. This point is called a reference point or origin.
Absolute rest is the concept that an object is not moving at all in relation to a fixed reference point, while absolute motion is the concept that an object is moving at a constant velocity in a straight line without any acceleration in relation to a fixed reference point. These concepts are foundational in classical physics but are not applicable in modern physics due to the theory of relativity.
What is the fixed reference point in the photos?
A line.
Without a fixed Point of Reference, there is nothing to be relative to.