Final answer:
An object that appears stationary and is used to describe the movement of another object is called a reference point or an inertial reference frame, fundamental to the study of Newton's first law of motion.
Step-by-step explanation:
Objects that appear to remain still and can be used to describe the movement of another object are known as reference points or inertial reference frames. According to Newton's first law of motion, an object at rest remains at rest, and an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced external force. This concept is fundamental to understanding motion and is used in one-dimensional kinematics to describe how an object moves in relation to another object.
In simpler terms, we use objects that we consider to be stationary as reference points to determine if and how other objects are moving. For instance, standing still on the sidewalk, we see cars passing by and say they are in motion because, relative to our stationary position, their location changes over time.
The inertial reference frame is a frame of reference where all objects follow the first law of motion, meaning they either remain at rest or move at a constant velocity in a straight line, unless acted upon by an external force.