Speed: a scalar(most important word to remember) quantity. It's a scalar because it has a magnitude, but no direction. Velocity is equivalent to speed, but with a direction, therefore, it is a vector(an equally important word to remember). An example: My velocity can be 300 mph north, where the magnitude of my velocity is 300 mph, and the direction is north, so, because it has a magnitude and direction, velocity is a vector. The second example: My speed is 300 mph, where the magnitude is 300 mph, but no direction was specified, therefore it is a scalar. Both your speed and velocity are defined as the time rate of change of your position in space. This pretty much means that both are how fast you move from one place to the other. Say your speed was 300 mph again, and you know that because there are two points on a map that are 300 miles apart, and it took you one hour to travel from one to the other. This means you could have gone 5000 mph for 2 minutes, then went 155.2 mph for 58 minutes, to arrive at the point 300 miles away after 1 hour. Or, you could have just traveled 300 miles per hour for the entire hour to reach the same point, in the same amount of time. You see that your overall speed between two points doesn't depend on how your speed changes between the two points.
Acceleration: a rate of change of a speed or velocity. That means that acceleration can be a scalar quantity or a vector quantity, meaning you can have an acceleration with a magnitude and a direction, or an acceleration with just a magnitude. This is what takes that change in speed into account. For example, say you start at 0 mph, and accelerate to 300 mph twice, once in 1 second, and once in 10 seconds. In the first case, you accelerate at 300 mph/second (~13.7 times the acceleration due to gravity or 13.4 Gs). In the second case, you accelerate at 30 mph/second (~1.37 Gs). In the first case, your eyes would possibly pop out of your head, and in the second case, you would hardly notice it. If you notice, in both cases, no direction was specified so the accelerations were scalars, but I could have just as easily said you accelerate from 0 mph north, to 300 mph north, and had vector accelerations.
So, the contest is looking for screenshots that would make your eyes pop out of your head.
