Agricultural extension was once known as the application of scientific research and new knowledge to agricultural practices through farmer education. The field of extension now encompasses a wider range of communication and learning activities organised for rural people by professionals from different disciplines, including agriculture, agricultural marketing, health, and business studies.

Extension practitioners can be found throughout the world, usually working for government agencies. They are represented by several professional organizations (such as APEN), networks (such as AGREN) and extension journals (such as Journal of Extension).

Agricultural extension agencies in developing countries have received large amounts of support from international development organisations such as the World Bank and the Food and Agriculture Organization(FAO) of the United Nations.