Medically Reviewed Everyday Health Carbohydrates are an essential part of a healthy diet, but it’s important to know they're not all created equal. How do you tell the difference between “good carbs” and “bad carbs”? The answer is both simple — and complex. Here’s everything you need to know about making smart carbohydrate choices. RELATED: A Carbohydrate Can Be a Simple Carb or a Complex Carb Carbohydrates, often referred to as just “carbs,” are your body's primary energy source, according to MedlinePlus. The three main types of carbohydrates are sugars, starches, and fiber. They're called “simple” or “complex” on the basis of their chemical makeup and what your body does with them. Because many foods contain one or more types of carbohydrates, it can be tricky to understand what’s healthy for you and what’s not.