There are three main types of carbohydrates in food: sugars, starches, and fiber. Sugars are simple carbohydrates found naturally in fruit and milk, and they are also added to foods such as candy, baked goods, and regular soda. Starches are complex carbohydrates found in beans, starchy vegetables such as potatoes and corn, and grains such as rice, oats, and wheat.
The body breaks sugars and most starches down into glucose, which it uses for energy. Fiber is the part of plant food the body does not break down. It comes in two forms: soluble fiber, which helps lower cholesterol and steady blood sugar, and insoluble fiber, which adds bulk to stool.
Source: MedlinePlus (U.S. National Library of Medicine): Carbohydrates
Image: Bread, rice, cornmeal, and pasta, Scott Bauer, U.S. Department of Agriculture, public domain, via Wikimedia Commons.