This is just a simple interface that allows students (hey! Is that you?) to explore the slope intercept form of a linear equation. Nothing fancy.
So, what happens if you set rise = 0? run? Can you use different values of rise and run to get the same slope? Why? [Hint: try setting rise to 1 and run to 2 and then rise to 2 and run to 4....] What happens when the sign of rise and run are the same? What happens when they are different?