Can someone explain whole grains?

What constitutes a whole grain? Is it a grain containing the germ and the bran? How do you know if both are present and intact? I was shopping for organic whole grains for the first time, and I was a little overwhelmed. I ended up buying millet, smelt, and rolled oats. The rolled oats I'll use in porridge, but how do I prepare the two other ones? All I know is they have to be soaked overnight for optimum digestion. Also, where and how should I store all three grains? If anyone could suggest a book, I would be relieved.