A food value chain is the full set of businesses and organisations that move food from production to the people who eat it: growers and fishers, processors and co-packers, storage and distribution, wholesalers, retailers, institutions and food service. The word "value" points to what each link adds, whether that is washing and packing produce, turning it into a product, or getting it to a buyer at the right time.
What distinguishes a value chain from a list of businesses is the relationships. Who supplies whom, who processes for whom, who partners with or funds whom: those links decide whether a small producer can reach a market or a new processor can find enough supply.
Regions map their food value chain to find gaps, such as a missing co-packer, cold storage out of reach, or growers with no route to local buyers, and to decide where a new facility, service or partnership would help most.