What is the difference between speed and velocity?

Speed is defined as the rate of change of motion of an object. In other words, it is the ratio of distance traveled to time taken.

speed = distance traveled by the object / time taken for the journey

In comparison, velocity is the rate of change of position of an object. In other words, it is the ratio of displacement to the time taken by an object.

Velocity = displacement of the object / time taken

Speed is a scalar quantity and only has a magnitude. In comparison, velocity is a vector quantity and has both magnitude and direction. 

Speed is dependent on the path taken by the object, since it is needed to determine the distance. Velocity is independent of the path taken by an object, since it depends on the displacement (distance between initial and final position of an object).

Hope this helps.