Velocity describes the speed and direction of an object. Speed tells how fast an object moves, but velocity is a vector measurement and includes both the rate and direction of an object's change of position.
The formula for calculating speed is distance traveled divided by time traveled. The formula for calculating velocity is the change of position, or displacement, divided by time. The difference between velocity and speed is more easily understood with the following example: a car completing a 10-mile course in 30 minutes has a speed of 20 miles per hour. If that car traveled at a speed of 20 miles per hour for five miles forward and then at the same speed for five miles in reverse, the velocity is zero because the car had no net displacement. It ended up in the same place it started.