The position of an object is where it sits on the number line. When the object moves to another position, its displacement is the second position minus the first position.
Δ x = x2 − x1
The word displacement implies we keep track of which way the movement occurs. In one dimension the direction is indicated by the sign: negative if to the left and positive if to the right. The word distance means how far the object moves regardless of direction. It is always positive and is equal to the absolute value, or magnitude, of the displacement.
If one follows the rule of always subtracting the first position from the second, the sign always works out to be positive if the displacement is to the right and negative if the displacement is to the left.