If you think all flours are created equal (a.k.a. you can use whichever kind is in your pantry for any given recipe), think again!
When one of our studio audience members named Antoinette asked "Cake Boss" Buddy Valastro about the differences between various flours, he laid down the baking law.
Q: What is the difference between different types of flour? - Antoinette
A: When you see "all-purpose," all-purpose is a bread flour as well. What happens is it’s refined a little bit differently, and a bread and an all-purpose flour has more gluten in it. So you would put a cake flour in a cake batter because it’s a smoother mouth feel. [Whereas] if you get a piece of bread, it’s more chewy -- that’s the gluten inside. So it [has] a higher protein level, which is really the difference. You should always [use the flour] that [the recipe] calls for, because there is a difference. Texturally, in your finished product, it makes a difference. - Buddy Valastro