DISPLACEMENT is the distance measured in a certain direction.
VELOCITY is the speed measured in a certain direction
Displacement is measured in the same units as distance and velocity has the same units as speed.
Displacement is given the symbol s, velocity the symbol v and time the symbol t.
It is important to realise that there is a difference between CONSTANT SPEED and CONSTANT VELOCITY. If a car is moving in a straight line at a constant speed then its velocity is also constant but if it turns a corner, still keeping its speed the same, its velocity will have changed because the direction in which it was moving has changed.