A change in displacement with respect to a change in time

The displacement of an object in relation to time is velocity.

Speed is similar, but it is actually the distance traveled in relation to time. The difference is that say if an object is spinning at one revolution per second, the speed of the edge is 'x' mps. The velocity on the other hand is 0 mps because the disk rotates at 1 rotation per second the displacement after one second is 0.