In science, speed is defined as the total distance traveled divided by the total time it took to travel that particular distance. Speed is dependent on the amount of time that it takes a person or object to move toward something.
When a car is traveling at a slow pace, it will take much longer for the car to reach a predetermined destination. This is an example of low speed. When the car accelerates and covers more distance in a shorter amount of time, the speed of the car is increased. The faster an object is able to go the distance that is desired, the quicker the speed. Miles per hour used is a good example of speed relating to distance.
Velocity is similar to speed, but is different because it measures the distance between where an object started and where it ended. An example would be a car driving in a circle. Even if the car was driving at a fast speed, the car would still end up in the same position that it started, making the velocity of the car zero. When velocity is measured, it is often referred to in a direction, depending on the displacement of the object.