The document defines ancient grains as grains that have changed little over hundreds of years compared to modern grains. It provides examples of ancient grains like quinoa, amaranth, teff, millet, and discusses their nutritional benefits. The document recommends getting at least half of daily grain intake from whole grains like ancient grains, provides recipes using grains like wheat berries and teff, and discusses how ancient grains are being incorporated into foods and beers today.