Farmers markets and other local markets allow direct marketing between producers, crafts people, artists etc, and their local community. They encourage a convivial, community based market where quality assurance is based on trust between buyers and producers. Producers are directly responsible for the quality of their produce, and buyers are directly responsible for offering a fair price for it.
The direct interaction between producers and consumers encourages a socially and environmentally embedded market. Farmers can directly answer questions about their production methods. Often food is available at farmers markets that is “organic” or biologically grown, that has no certification, but if consumers know the producer and the producer’s values and approaches to agriculture, no such certification is needed. Food available can generally be expected to be super-fresh, as it generally has not needed to travel far at all to market. Locally produced food makes a lot of sense in terms of energy efficiency for the same reason.