Carbohydrates are food macronutrients that the body converts to glucose to fuel itself. If you consume more carbs than your body actually requires, it stores some of those carbs as glycogen in the liver and muscles and the remainder as fat.
Followers of low-carb diets count grams of carbs rather than calories and are ultimately concerned only with net carbs.
Counting Net Carbs
Low-carb diets limit the dieter to a certain amount of carbs per day, considerably below the general recommendation of carbs. A low-carb dieter achieves this goal by choosing freely from meats, fish, eggs and fats, which contain no carbs, and supplementing those foods with controlled portions of vegetables, certain fruits, nuts and dairy products, which generally provide low net carbs.
The formula to counting Net Carbs:
Total carbohydrates per serving
minus number of grams of fiber (soluble and insoluble) per serving
minus 1/2 the number of grams of sugar alcohols if 5 or more from total carbohydrates
equals net carbs