I've heard of different kinds of flour like rye, spelt, etc but I didn't know what they were. So, I looked it up. Here's the skinny:
All purpose flour has a medium protein content that makes it suitable for most baking uses.
This flour is made from the fleshy root stock of the tropical arrowroot plant. Its white, fine, and powdery texture is very similar to cornstarch but it has no flavor at all. It is typically used as a thickener for puddings, sauces and other cooked foods.
Barley flour is made from barley ground very finely. It is rich in protein, calcium, phosphorus, potassium, iron, and B vitamins.
Made easily by grinding all types of beans, this flour can be used to enhance the flavor and health benefits of your breads, and they also make easy soups and dips.
The best flour for bread making, it is ground from hard wheat. It has a high protein (gluten) and low starch content.
Brown Rice Flour
Ground from brown rice, this flour has a slightly sweet flavor. It is used alone or combined with wheat flour in breads and batters.
Buckwheat flour is ground from the seeds of a plant originating in Asia, has an earthy, slightly sour flavor that is usually tempered in commercial products by the addition of a little wheat flour.
A yellow, finely ground version of cornmeal, corn flour is used to add a mild corn taste and a pleasing texture to baked goods.
Made from a small round grain resembling mustard seed, this flour has a slight nutty flavor.
Oat flour is a fine flour ground from dried oats, has a characteristic nutlike flavor. It is used in combination with wheat flour.
Pastry and Cake Flours
Pastry flour is lighter and has a lower protein level of ~9-10% as opposed to ~ 12-13% found in bread flour. The soft, flakiness of pie crust is attributable to the softer flour. Cake flour is lighter than all purpose flour.
This is a gluten-free flour made from cooked, dried and ground potatoes. It is mostly used as a thickener. It is also known as potato starch.
This very fine powdery flour is made from pulverized long-grain or glutinous rice, used to thicken cakes and puddings as well as to make noodles and very fluffy breads.
Rye flour is a fine flour ground from grains of rye grass, a close relative of wheat. It has a slightly sweet-sour flavor.
Self Rising Flour
Self-rising flour contains 1 1/2 teaspoons baking powder and 1/2 teaspoon salt for each cup of flour.
Semolina flour is made from the finely ground endosperm of Durum wheat. Usually used in pasta making, it is a tasty, high protein addition to breads.
Seven-grain (or nine-grain) Flour
Seven-grain flour is a commercial blend commonly made up of millet, rye, corn, wheat, barley, oats, and flax or triticale. It is found in health-food stores and well-stocked markets.
This flour is lighter in protein and more easily digested than regular wheat flours. This flour is sometimes known as Farro.
Whole Wheat Flour
Whole wheat four is made from milling the entire wheat berry. it is brownish in color.
This was slightly adapted from here.
Now you know! So the next time someone tries to get fancy and talk about spelt flour you can join in.