And this basically means that initially most of our active sites on our enzymes are actually empty. Now, as we begin to increase the amount of substrate as we begin to increase the concentration of our substrate more and more of the active sites will be occupied, will be filled and that will increase the overall rate of our reaction. Eventually, however, we will reach a point at which all the active sites on all our enzymes are filled. At that point, our reaction, our enzyme activity, has reached a maximum rate and this is known as the maximum velocity or VMAX. And the enzyme at this point is said to be saturated. And by increasing the concentration of substrate at this point we are basically not affecting the rate of our activity of the enzyme because all those active sites of all the enzymes are actually filled up or occupied.