This question involves a few entities namely Length, Distance, and Displacement
What is Displacement: Displacement is the shortest distance from starting position to the ending position.
I have tried to explain with a diagram. The green line is the displacement where as the dotted black line is the distance (path length).
So when the path from point A to B is curved then if you follow the curved path which is the distance and if you want to calculate the displacement it will be a straight line from point A to point B.
Now in our question difference between path length and displacement note that path length is also the distance. So the difference between path length and displacement is the same as distance and displacement.
What is the difference between path length and distance?
Both are Same
Is displacement a Vector?