The term velocity is often confused with speed; to understand the concept of velocity, it is helpful to first understand what is meant by speed.Average speed is determined by dividing the distance traveled by the time required to move that distance. If a car travels 50 miles in one hour, its average speed is 50 miles/one hour, or 50 miles per hour. Given the average speed that a body is traveling, the distance it travels is the product of its average speed and the time traveled. Thus, if the aforementioned car travels at 50 miles per hour travels for two hours, the distance traveled is 100 miles. It is more often the case, however, when a car is traveling between two points, that it will slow down or speed up to accommodate road conditions. For this reason, it is sometimes more helpful to speak of the car's instantaneous speed, which is the speed that the car is traveling at a given point on the trip.

The difference between velocity and speed is that speed only takes into account the distance that a body travels in a given time (i.e., rate of travel), while velocity takes into account the direction traveled as well as the travel speed. This is an important distinction. To the driver of an automobile traveling from San Francisco to New York, the average speed of the trip, which can easily be computed by dividing the mileage shown on the odometer by the travel time, is likely to be of more significance than the velocity. But to a weather forecaster, a storm front traveling 100 mph from the northeast is significantly different from one traveling at the same speed from the southwest; thus it is the velocity that is important in this case.