Velocity and Acceleration

Journal 1: In this picture, we can see a glimpse of what Acceleration and Velocity are. Acceleration is "the change in velocity," according to Dictionary.com, or in scientific terms, the equation is Velocity/change in time <-(m/s^2). In this photo, I am just simply walking on a treadmill at a constant speed of 2 (2 is according to the treadmill, unsure of actual speed). Yet when I pressed 3 or anything higher, my acceleration increased, then maintained constant 0 at that newly selected level once adjusted. Until I select a different level, at that moment the acceleration will change. On a graph, acceleration is always horizontal. Velocity is slightly different. Graph wise, a velocity graph can be horizontal, diagonal, but never curved. Velocity is the "rapidity of motion or operation," according to Dictionary.com, but may I also add that direction does matter too, or else it would be speed and not velocity. Velocity is measured by the equation: change in displacement/change in time <-(m/s). Here, my velocity is sadly 0, since my displacement is 0, and I am moving in place. This applies to acceleration as well, that displacement does affect the answer. But say I did move forward, I would be moving in a positive direction for both cases. I would gain Velocity as I moved away from my original point. If i ran at 4mph, I would constantly be moving up the velocity graph, and when I stopped, I would form a horizontal line at that position. Then if i turned 180 degrees and went back at 5mph, my line according to the graph will begin to go towards negative (downward) at a sharper angle (greater slope) than when I was walking forward at 4mph. This is just a simple glimpse at Acceleration and Velocity.