It’s a ratio of where you get your calories from. Depending on the desired result you change the percentages…fat, carbs, protein. For each gram of fat you eat you get 9 calories. Carbs and protein are 4 calories per gram. So if you ate 50g of fat (x9=450 cal) 100g of protein (x4=400 cal) and 150g of carbs (x4=600 cal) your total calories would be 1450. If you did keto for example you would eat like 100g fat (900 cal) 80g protein (320 cal) and 30g carbs (120 cal). It still equals 1440 calories but you changed your “macros”.