what is not moving; fixed?
I do not understand your question. Whether or not something is moving or not moving depends upon the coordinate syatem you are using to measure the location.
If you are standing inside a moving elevator, you are fixed with respect to the elevator but moviong with respect to the building and earth.
Buildings are fixed with respect to the Earth but are rotating about its axis.
According to the theory of relativity, there is no such thing as absolute velocity.
"Fixed" refers to something that is stationary or immobile, or does not change its position or location. In the context of objects or structures, being fixed means being securely attached or fastened in place.
To determine whether something is fixed or not, you can observe if it remains stationary over time or if it is securely attached to another object. Some examples of fixed objects are buildings, statues, or objects that are firmly fixed to a wall or floor, such as shelves or hooks.
On the other hand, if something is not fixed, it is movable or able to change its position freely. Examples of non-fixed objects include vehicles, people, or any object that can be easily moved or relocated.
To identify whether an object is fixed or not, you can use visual observation and common sense. If an object is firmly attached or does not move despite external forces, it is likely fixed. Conversely, if an object is capable of being moved or does not remain in one position, it is not fixed.