the forces of supply and demand help determine the equilibrium quantity and price at which a product will be sold i.e. there is no government intervention regarding quantity or prices for goods & services
In pure competition (or a perfectly competitive market), the market is saturated with consumers and suppliers.This means that the selling price in the market is purely determined by the intersection between demand and supply (the price at which the quantity of the good/service consumers want to buy equals to the quantity of the good/service suppliers want to supply). This is because if a supplier wanted to sell above the market price, consumers would just acquire the good from their competitors since there are many other suppliers of the same good/service. Similarly, consumers would be turned down if they suggested a lower price because there are many other consumers who want the good/service in the saturated market.