One of the most asked questions from gluten free novices is "Can gluten free flours be substituted for wheat flour one-for-one"? The short answer is that gluten free flours do not substitute one for one with wheat - however, gluten free blends can. Let me explain.
Gluten is what gives wheat elasticity and thus provides that chewy, doughy texture. Gluten also retain gases during the baking process which enables dough to rise, makes it stronger and less likely to collapse. That combined with it's light crumb is what makes wheat the "perfect" grain and why many of those who came before us worked exclusively with it. No other flour combines all those properties into one the way wheat does. So, in order to recreate those properties, we must combine flours and make blends. By combining a grain (brown rice, sorghum, millet, etc) with a starch (corn, potato, tapioca, etc), we are able to imitate wheat by having the grain (flavor and nutrients) and the chew (from the starch). Better yet, if we combine multiple grains and multiple starches, we get even closer to wheat because each grain and starch has their own unique properties and "bring something to the table" so to speak. There are a plethora of other types of flours like bean flours, coconut flour and nut flours and those all have different properties that they can lend too. Finally, we can give flour blends a "stretch" factor and help them bind and emulsify together better by adding xanthan or guar gum. Very little is needed and it adds yet another wheat-like property to gluten free baked goods. So, a blend of flours and starches can mimic wheat and can be replaced one-for-one whereas a single gluten free flour (only brown rice or only sorghum, etc) does not have all the properties needed to replace wheat on its own.
While understanding and learning about all the different flours can be intimidating and difficult at first, the sheer variety provides numerous opportunities for creativity, an assortment of flavors, and ensures that there will be at least one blend that you will enjoy. Personally, my favorite all-purpose mix is this one, though I freely admit that I'm probably just a bit biased since I created taht mix myself! ;)