Rice bran is the hard outer layer of the rice kernel. It is a byproduct of the milling process that converts brown rice to white rice. See more at bran.
Rice bran contains approximately 13% oil, and can be pressed to produce rice bran oil.
Rice bran is used extensively in Japan, where it is called nuka. A mash of rice bran is used to produce the common pickles called nukazuke. It is added to water when boiling bamboo shoots, and is used to stew fish.