Rice bran is made from the outer layer of a grain of rice and full of nutrients and fiber. It’s a byproduct of the rice milling process, an in Korea you can buy it from your local mill in huge quantities, very cheaply. In the West you can buy it in specialty food shops or at Amazon.com.
My cookbooks
Which to get? my first book has all the recipes for all the essential Korean pastes and sauces, but my second book Maangchi's Big Book of Korean Cooking has more recipes. Both are best sellers and either one is a good choice if you want to learn Korean home cooking.