In physics, (basically) everything is relative. That is, if we pick one point in space to be our starting point for something, it could have been any other point. A reference point is that a arbitrarily selected point in space that is used as a reference, or to relate to something else.
An example would be an object’s displacement, which is the distance from the location where an object begins to move (the reference point) to the place where it stopped moving. This requires us to plot a point in some space where we reference later, when we find the object’s ending position.
