Why micronutrients and macronutrients are called so ?  What role do they play?

These elements are obtained from air and from soil, dissolved in water.

Micronutrients - are elements required by plants in very small quantities to be utilized for their growth and development process.

These are seven elements namely, Boron, Chlorine, Zinc, Copper, Molybdenum, Iron and Manganese.

Macronutrients: are elements required by the plant in large quantities for their growth and development.

These are nine elements namely - Nitrogen, Phosphorus, Potassium, Hydrogen, Carbon, Oxygen,Calcium, Magnesium and Sulfur