Cooking Pasta Dishes

I never really understood why you add the pasta water to the pasta dish you just finished tossing together.  Now I know.  If you  cook your pasta the way we are supposed to, it should be a little underdone.  Then, before draining it, save 2 cups of pasta water and drain the rest.  As the pasta sits in the strainer, it will continue to cook a bit.  Then as you combine the pasta with whatever sauce you have made up, add the pasta water in small increments and it helps maintain the consistency of the sauce.  If you don't add the water as you toss, the pasta will draw whatever liquid is in the sauce out and dry out your creamy sauce.  You don't need to use all of the water, just use what you need to maintain the integrity of the dish.