This is the same graph we focused on many times in previous lectures. And so on this graph, the x axis is a substrate concentration and the y axis is the velocity, is the rate at which the enzyme actually operates on that specific substrate. And what the blue curve describes is how the rate, the velocity of that enzyme changes as we increase the substrate concentration in the environment. So as we increase at the beginning we see that there is a linear increase. So that means the velocity is directly proportional to the concentration of S. But then the rate slowly begins to decrease, the slope decreases and it levels off and eventually it reaches a maximum velocity. And that is given by this horizontal green line.