The chessboard has 64 squares, they are distributed in 8 by 8 squares. if we call the bottom-left square (1,1), we can identify (3,2), (5,1) and (6,3) as:
It means that the translation made when the knight moves from the location (3, 2) to (5, 1) is two squares to the right and one square down.
In the same way, the translation made when the knight moves from the location (5, 1) to (6, 3) is one square to the right and two squares up.