The yellow or gold crosshair lines show how the line relates a specific value of X to a specific value of Y. From the value of X, draw a vertical crosshair up to the blue line. From there, draw a horizontal crosshair to the Y-axis and read off the value Y that is related to the value of X by blue line. This is the same as doing the calculations specified by the equation of the line: That is, take the value of X and multiply it by the value of the slope; then, add the intercept to get the value of Y that is related to the value of X. The other parts of the graph work just as before. Here again is the explanation about the intercept and slope parameters and how to change them.