The three graphs above all represent the same action, throwing a ball up and catching it above a motion sensor.  The red line is a Position vs Time graph, the green is Velocity vs Time, and the blue is Acceleration vs Time. They all have the same "fast, slow, stop, slow, fast" motion to them, just shown in different graphs and lines. As the ball is released when you toss it up, it’s moving at the fastest velocity. As it continues upwards, it begins to slow down, before reaching it’s stopping and highest point. When it begins it’s descent, it starts off slower and gets faster again as you catch it. The blue line is horizontal because it represents the acceleration, which is steady throughout because the acceleration is always based off of gravity, which is 9.8 m/s on planet Earth.