Food systems refer to the rules of functioning, the modes of organization, the technologies and practices that determines the ways in which food is consumed, produced, transformed, packed, and distributed along food chains.  Food systems can include the management of alimentary wastes or residues. But they should exclude coproducts sold in non-alimentary markets. Food systems shape the quality of goods produced and consumed, and how consumers can access to foodstuffs. They also determine their nutritional quality. As a result, food systems fulfill societal functions, such as contributing to and promoting a sustainable development of human societies.

According the experts group on food security and nutrition of the United Nations, sustainable food systems should guarantee a fair access to nutritional food to everyone without compromising the economic, social and environmental ability of future generations to ensure their own food and nutritional security. FAO sustainable food systems should: i) protect ecosystem biodiversity; ii) be accessible and culturally acceptable; iii) be economically fair and affordable; iv) be safe, nutritionally adequate, and healthy; and v) optimises natural and human resource use, in particular by cutting losses and wastes in food systems.

Currently, very diverse food systems coexist. On the one hand, standardized raw materials and food products are produced and traded in global food systems. On the other hand, global food systems are generally opposed to territorialized food systems. The main purpose of agroecology is to provide food security to territories while contributing both to their social sustainability and to the well-being of populations. To the end, agroecology leans on landscape functionalities or on local biodiversity. Agroecology also produces localized ecosystem services. Accordingly, agroecology, while being embedded into territorialized food systems, is meant to promote the sustainability of food systems.