Calories are a measure of the energy value of foods. "Empty calories" are calories that will give you energy but little else in the way of nutrients that your body needs. It's better to eat foods that give you other good things that your body needs, not just empty calories.
Are you consuming a lot of empty calories? Candy and sodas have lots of calories and very little, if any, nutrients. Most of the calories in soda come from added sugar.
How much sugar is okay? The World Health Organization says you should limit sugar to five percent of your daily calories. For kids between the ages of six and eleven, that's about 5 teaspoons or 21 grams a day. One kind of soda has 52 grams in a 12 ounce can. That's more than 12 teaspoons of sugar!