A calorie is a unit of energy. Most people only associate calories with food and drink, but anything that contains energy has calories. 1 kilogram (kg) of coal, for example, contains 7,000,000 calories.
In nutrition, calories refer to the energy people get from the food and drink they consume, and the energy they use in physical activity.
It is generally accepted that the average man needs 2,700 kcal per day and the average woman needs 2,200 kcal per day. You can find the calorie breakdown for purchased food items especially snacks in the nutritional information on all food packaging.
You may be either trying to increase your calories to gain weight or reduce them to lose weight. Which ever one you are trying to achieve, we have something for you.