The circular flow model describes the reciprocal flow of income between two main sectors: households and firms. Households provide factors of production like labor, capital, and land to firms, and in turn receive income payments from firms. Firms then use these factors to produce goods and services, which they sell to households. Households use their income to purchase goods and services from firms, completing the circular flow. Money facilitates the exchange of goods, services, and income between the two sectors.