As most of the things in the world are scarce, the allocation of these scarce resources becomes very important. Economics, whether micro or macro, is needed because of this scarcity.
Microeconomics deals with individuals and firms. Microeconomics can also be termed as the study of supply and demand. It assumes rational behavior of consumers and perfect competition to make mathematical models.
A perfectly competitive market adjusts the prices of goods and services by itself without any external intervention. It also makes the business feasible for all the players. Both the supply and demand are controlled by the price.
Businesses use several micro-economic concepts to make important decisions like whether to expand or shrink the quantity produced, how to maximize the profit, etc. The ultimate objective of buyers and sellers is to maximize the utility.