Macros is just short for macro-nutrients. Your body needs nutrients to work correctly and to be healthy. There are six different nutrients your body needs, three micro and three macro Nutrients.
The Macro-nutrients are fat, carbohydrates and protein.
Your body needs all three to work correctly. The brain prefers Carbohydrates as energy, especially for athletic type of activities. Fat is used for energy during exercise but also during rest. Protein helps build and maintain muscle. How much of each is needed though differs from person to person.
When someone is talking about tracking macros, they are referring to keeping track of how much protein, fat and carbs they are eating.
All three give you energy.
So for every 1g of protein you consume it = 4 calories
for every 1g of carbohydrates it = 4 calories
and for every 1 g of fat it = 9 calories
So basically if someone is counting macros and they eat 200g carbs, 60g fat and 150g Protein then that means they are eating:
200g carbs x 4 calories= 800 calories, if you eat 200g of carbs, you just ate 800 calories!
150g protein x 4 calories= 600 calories
60g fat x 4 calories= 240 calories
I tried to make this simple to to answer the basic what are people doing or meaning when they are talking about tracking macros. I hope this was helpful, let me know if you have any questions by leaving hem in the comment section below!
*Disclaimer: The above example is only A REALLY RANDOM EXAMPLE don't try and use it for yourself.