The phrase "less calories" refers to a food or beverage that contains fewer calories than other similar items. Calories are a measure of energy, and they indicate how much heat can be generated from consuming a certain amount of food. When something is described as having less calories, it means that the item has fewer calories per serving compared to other options in its category or brand. This could make it an attractive option for people who are trying to maintain a healthy diet and limit their daily calorie intake.