The demand for a product will influence its price and will influence the incentives for the seller. If the demand is not fulfilled yet, the price will rise and the seller will have incentives to make more products. If the product made is more than demand, the price will decrease and the seller will make less product.
This interaction will eventually lead to a condition where the amount of product is equal to demand. This condition is called market equilibrium. The price at this condition will relatively stable and won't change much.
