From the FarmPlate glossary:

The term organic describes a set of agricultural principles and practices that attempt to capture the energy and nutrients of natural systems for food production. Organic food production fosters the cycling of resources, promotes ecological balance and conserves biodiversity. This was the primary type of agriculture until the rise of industrial agriculture in the mid-1900s. Effective since 2002, the National Organic Standard (NOS) is the “organic rule” that individual inspectors use across the United States to determine compliance. Today’s organic movement rejects the use of synthetic or chemical fertilizers, pesticides and herbicides as well as genetically modified organisms (GMOs). Sub-therapeutic hormones and antibiotics are not administered in organic animal production. For assurance that products have been produced with organic methods, look for the USDA Certified Organic seal on products. A number of certifying agents decide which farms, processors and handlers meet current USDA organic standards.