Distance and Displacement
Distance is a scalar quantity representing the interval between two points. It is just the magnitude of the interval. However, displacement is a vector quantity and can be defined by using distance concept. It can be defined as distance between the initial point and final point of an object.
So if Mr. K suddenly decides to run from A to B to C to D to E to F to G to H to I all the way back to A, he would have traveled quite a distance (the perimeter of polygon ABCFEFGHI to be exact), but would have zero displacement.
Similarly, if Jackie had decided to run the lap himself, but gave up at point E, he would have a distance of the sum of line segments AB, BC, CD, and DE, but his displacement would only be the length of segment AE.
Similarly, if Jackie had decided to run the lap himself, but gave up at point E, he would have a distance of the sum of line segments AB, BC, CD, and DE, but his displacement would only be the length of segment AE.