In economics a resource is defined as a service or other asset used to produce goods and services that meet human needs and wants. Economics itself has been defined as the study of how society manages its scarce resources. Classical economics recognizes three categories of resources, also referred to as factors of production: land, labour, and capital. Land includes all natural resources and is viewed as both the site of production and the source of raw materials. Labor or human resources consists of human effort provided in the creation of products, paid in wage. Capital consists of human-made goods or means of production (machinery, buildings, and other infrastructure) used in the production of other goods and services, paid in interest.