Speed:

(i) Speed is simply the rate of change of motion.

(ii) Speed is the distance traveled by a body in a  unit time.

(iii) Speed is a scalar quantity.

(iv) Speed ascertains how fast a body moves.

Velocity: 

(i) Velocity is direction-aware and it is the rate of change of position of an object.

(ii) Velocity is the displacement covered by a body in a unit time.

(iii) Velocity is a vector quantity.

(iv) Velocity ascertains the object’s speed and the direction it takes while moving.