What is the difference between calories from fat and just calories, on a food label?

Total vs. Fat kcal. On food labels, "calories" stands for total kcal obtained from fat, 9 kcal/g, carbohydrates, 4 kcal/g, protein, 4 kcal/g, and/or alcohol, 7 kcal/g. "Calories from fat" means just that. Because of the detrimental effect on overall health and heart disease risk, total fat calories should be less than 30% of your total daily caloric intake, or roughly 600 kcal if you consume 2,000 kcal each day.
Other sources. There are also calories from proteins and carbohydrates.