Final answer:
A reference point allows people to gauge the relative speed of an object by comparing its motion to that of another object.
Step-by-step explanation:
When using a reference point to compare how fast something moves relative to another object, people can gauge the relative speed of an object. This means that, with respect to the reference point, they can determine how fast one object is moving in comparison to another. This concept of relative speed is crucial because it helps to understand the motion of objects in different frames of reference. This is a key principle in physics, where the position, velocity, and acceleration of an object are described relative to a chosen frame of reference.