Distance cannot be negative and distance traveled never decreases. Distance is a scalar quantity or a magnitude, whereas displacement and position are both vector quantities with both magnitude and direction.

      The distance covered by a vehicle (for example as recorded by an odometer), person, animal, or object along a curved path from a point A to a point B should be distinguished from the straight line distance from A to B. For example whatever the distance covered during a round trip from A to B and back to A, the displacement is zero as start and end points coincide. In general the straight line distance does not equal distance traveled, except for journeys in a straight line.

Definition provided by Wikispedia 



     A vector that locates an object in reference to an origin 

  Example: The point A is 5 meters in the X direction and 3 meters in the Y direction. 

     Unlike distance, position, like all vectors can have negative values.

Example:  If the position of A was 5 meters in the X direction and -3 meters in the Y direction, the "dot" A would be below the X axis instead of above


   Displacement is a measurement of change in position of an object in motion. Its magnitude and direction are measured by the length and direction of the straight line joining initial and final positions of the particle. Obviously, the length of the straight line between the positions is the shortest distance between the points.

    In order to illustrate the underlying concept of displacement, let us consider the motion of a particle from A to B to C. The displacement vector is represented by the vector AC and its magnitude by the length of AC.