Cake Flour: Flour used for cake. Has the least gluten content to produce delicate cake. Typically is bleached to create pristine white cake. 6-7% protein. I have only ever been able to buy cake flour in a box (about 2 pounds) but unless you make cake all the time, this much should suffice.
All Purpose Flour: Like the name suggests, this is the flour used for almost everything in your kitchen. Almost every person I know has a bag of AP flour floating around even if they don't cook. You can find it bleached or unbleached. 9.5-11.5% protein. If you use all purpose flour instead of cake flour in a recipe, your end product will typically end up heavier and more dense from the increased protein.
Pastry Flour: Less protein than AP flour but more than cake flour. Ideal for (duh) pastry. Pie crust becomes much easier if you get/make yourself some pastry flour. If you don't want to buy pastry flour, you can make an acceptable substitute by mixing cake flour and AP flour in a 1:1 ratio. 7.5-9.5% protein.
Whole Wheat Flour:
Whole wheat flour is made by crushing the whole wheat berry. Because it has more oils, it can go go bad faster. If you don't use it very much, store your whole wheat flour in the freezer. When a recipe calls for all-purpose flour, I like to substitute out 1 cup of all-purpose flour and replace it with 1 cup whole wheat flour to increase the nutritional value. Substituting 100% whole wheat for all-purpose will result in a heavier baked good due to the increased protein although I have had much success with substituting up to half of the all-purpose flour with whole wheat flour.
- Red Whole Wheat Flour: made from red wheat, has a higher protein content that white whole wheat flour. In the United States, red whole wheat flour is more prevalent.
- White Whole Wheat Flour: made from hard white spring wheat. Has a lower protein and gluten content than red whole wheat flour. Because of it's softer nature, it can be used more like all-purpose flour but with higher nutritional content.
Bread Flour: Has the greatest protein content. Protein content in the flour is what makes gluten. Used to make bread because unlike cake, you want your bread dough to be more stretchy and elastic. 11.5-13.5 % protein. You can buy it bleached or unbleached.