In this model [circular-flow diagram], the economy is simplified to include only two types of decision makers—firms and households. Firms produce goods and services using inputs, such as labor, land, and capital (buildings and machines). These inputs are called the factors of production. Households own the factors of production and consume all the goods and services that the firms produce.

p. 22 - Principles of Economics (2015) - Ch. 2. Thinking Like an Economist