Calorie count

"Macros" refers to your portion of carbs, fats, and protein you consume in a day. These are given in grams. 1g of carbs and protein is equivalent to 4 kcals (aka "calories") of energy. 1g of fat is equal to 9 kcals of energy. There are recommended amounts of carbs, protein, and fat that you should eat in a day based on your body weight (though you can customize these values if you are doing low-fat, high protein, low carb, diets, etc)

Each pound of fat is approximately 3000 calories. So if you want to lose 1 lb a week, MFP recommends you cut your daily intake of calories by 500 calories a day (500 calories a day x 7 = 3500 or 1 lb of weight lost a week).

Any exercise calories are added to your daily value. So if you are recommended to eat 1500 calories a day and do 500 calories of exercise, you have "earned" an additional 500 calories that you can eat over the course of the day and still lose that 1 lb a week (So on that day, you could eat 2000 calories and still be in a calorie deficit to be on track to lose weight).

You can also customize your chart to show you daily amounts of sodium, certain vitamins, or fiber, depending on what are your nutritional goals.

I hope that helped!