Answer:
Speed is a scalar quantity, when we know the speed we only know the magnitude but not the direction, we don't know if the object is going forward or not. Therefore, the disadvantage of speed is that we don't know the direction.
On the other hand, velocity is a vector quantity, so with the velocity, we have the magnitude and the direction, so we know the speed, this is, the distance traveled per unit of time, and we know the direction of this speed. Therefore, the velocity gives more information about the movement of an object.