This is a good question. Grain is the seeds of various grasses. This includes Wheat, rye, oats, rice and barley. You will hear them called "the staff of life" because many of the cultures of the world live on grains to survive.
A grain of wheat contains three layers. The germ is the heart and it will sprout when the grain is planted. This is rich in B vitamins, vitamin E and some fats and proteins. You can count iron which is a mineral in this list.
The endosperm is the largest part of the grain, it is mostly carbohydrates, some vitamins and minerals.
The bran is the covering of the grain, it is mostly fiber with a trace of B vitamins and likewise a trace of iron.
Because of the fats in the the heart layer the grain, once ground, will begin to go rancid. This is the off taste in whole wheat flour that isn't used fast enough. I would put your bag of whole wheat flour in a freezer bag and keep that flour in the fridge or freezer to avoid that rancid taste. Or as I do I grind it and use it right away. I have the Vitamix grain container and it will grind a little over a cup at a time. On top of the rancid taste there is a mold that will grow in old flours that can be dangerous.
White flour has the bran and the germ removed for long storage. This also removes the healthy part of the grain. That is why you will see the term "enriched" on white flour products. This is the best reason for using whole grains, nothing taken out! Nothing lost in the removal. I did ask you to knead and form your bread on white flour if you had it. The reason is that without the bran it won't stick to you or the dough so much, the bran grabs and holds to what it touches.
The bran or covering of the grain is sharp and it is the reason whole wheat bread can be flat, the bran can cut through the stretching gluten. We've done our best to get around it in the recipe below by really heavily developing the gluten and using a short raising time with a large amount of yeast. It's a wonderful loaf of bread, compare it with other recipes you have used. The loafs can fall apart easy (not enough gluten threads holding things together and bran cutting through). I think my favorite use of whole wheat flours is flat breads. The worlds cultures have long ago perfected flat breads all we need is to learn how and in minutes you can make a pita, a Naan, a chapati, etc. I would make it my hobby to learn to make flat breads to go with my food storage. It is the fastest, easier bread known to mankind! Would you like some recipes? If you learn to make flat breads you can take any grain in the world and make something good to eat from it. Another thing you may not know about wheat is that it is used as the following foods, bulgur (cracked wheat), Couscous made from Semolina which is the inner, granular, starchy endosperm of hard or durum wheat (not yet ground into flour); used to make pasta and semolina milk pudding. It is the gritty, coarse particles of wheat left after the finer flour has been extracted. Can you think of some other ways in which wheat is used besides flour? I will follow up this blog with a list of exactly what is in each grain of wheat. My first Vegetarian cook book I used (started in the early 1970's) tells you to make sure every day has a large variety of foods. Don't serve two dishes using the same food. I can see that if you want to get the best chance at health you need a lot of different vitamins, minerals etc. This never serving two of the same foods in a day insures that. Any more questions of wheat? Really just a seed even if in it's whole form it is sometimes called a berry, it is really a kernel!