Go to the baking section of any grocery store and you will see a number of types of flour; a trip to a baking specialty store will reveal many more. Each type of flour achieves different results. All-purpose flour--the kind that most non-chefs use in their kitchens--comes from the wheat kernel's most finely-ground component. It includes both soft and hard wheat, making it appropriate for almost any kind of baking.
Bread flour is similar in makeup to all-purpose flour, but its higher levels of protein help to create a denser, chewier loaf. Cake flour, by contrast, is made up of soft wheat only and contains fewer proteins, yielding light, fluffy results.
Pastry flour, also a soft flour product, is slightly higher in protein and therefore appropriate for cookies and other baked goods as well as cakes. Self-rising flour, commonly found in quick breads and biscuits, includes baking powder and salt for added convenience. Finally, harder types of flour, such as semolina and durum flour, are more commonly used for pasta making.