Can someone explain macros?

When people refer to macros, they mean macronutrients. You have 3 different macronutrients: carbohydrates, protein, and fats. Things like vitamin A, vitamin B, iron, etc. are referred to as micronutrients.

I'm assuming you've heard of macros as in if it fits your macros (iifym) or flexible dieting. This is a style of eating where one counts the grams of carbs, protein, and fats rather than calories. The general theory behind it is as long as you are 'hitting your macros' (i.e. getting your target grams of protein, carbs, and fats) and your micronutrients you can eat whatever type of food you want.