Grains provide complex carbohydrates, also called starches, which supply energy. Whole grains are more nutritious than refined grains because nutrients have not been lost in processing. Some nutrients have been added back to refined grains, but often not all the nutrients which were lost are added back.
Grains are the seed-bearing fruits of grasses.
An inedible husk, also called chaff, is the outermost layer of the grain. The next layer of a grain is the bran, a protective coating. This layer is rich in fiber. When this layer is removed, the product may be described as pearled or polished. When grains are refined, the husk, bran, and germ are removed leaving only the endosperm.