A vector is a mathematical quantity that possesses both magnitude/length and direction (indicated by an arrow head). A vector comprises a horizontal shift as well as a vertical shift. Horizontal shifts to the right are postive (+) while shifts to the left are negative (-). Similarly, vertical shifts upward are positive (+) and downward shifts are negative (-).

In the interactive applet below, see if you can determine the horizontal and vertical shifts in moving from point A to point B in order to see the corresponding vector.