Macronutrients are elements which plants require in relatively large amounts. The following elements are categorized as macro nutrients; Nitrogen (N), Phosphorous (P) and Potassium (K).
These are nutrients that plants require in smaller quantities than nitrogen, phosphorus, and potassium while on the other hand; plants require these nutrients in larger quantities than the micronutrients. The following elements are categorized as secondary nutrients: magnesium, calcium and sulfur.
Micronutrients are nutrients that are required by plants and other living organisms in small amount. Not to say they are not important but required in small amount.