Simple carbohydrates (extracted)
Sugars are "simple" carbohydrates. They are closest to the completely broken down form that your body uses as fuel. In fact, glucose itself is the simplest sugar. So the body converts sugar directly into usable energy. Pure sugar foods, such as hard candies and soft drinks, raise your blood sugar level and your energy level temporarily -- sometimes called a "sugar high." However, the levels quickly drop below what they were before, in a rebound effect. This has been dubbed the "sugar blues."
Sugar's reputation is truly battle scarred, but with very little reason. Sugar isn't quite the evil substance you may think it is. Its biggest fault is with the company it keeps; it is often found in foods with little or no nutritional value.

Complex carbohydrates (extracted)
Complex carbohydrates -- found in bread, pasta, potatoes, rice, starchy vegetables, oatmeal, and dry beans -- are the basis of a healthful diet.
These starches are better than the simple sugars for many reasons. One reason is that they are absorbed more slowly (good for blood sugar control), but their real advantage is that they are found in foods that contain many other nutrients. Unlike sugars, which are either by themselves providing empty calories or worse, paired with tons of fat, complex carbohydrates are found in grain products and vegetables that provide many important vitamins and minerals.
What's more, a diet based on complex carbohydrates has significant disease-prevention qualities. By getting the bulk of your calories from foods rich in complex carbohydrates, you decrease your risk of many diseases, including heart disease, high blood pressure, stroke, and certain types of cancer.