Rice flour is simply flour made from rice, so not a substitute for rice at all. However the trick is to see the other word in “rice flour”, which is not rice, but flour. Hence, “rice” is a descriptor of “flour” and we can look at types of flour, thus rice flour is a substitute for wheat flour, which contains gluten.
Thus, rice flour is often a substitute for wheat flout for gluten intolerant people.
Rice flour is often used in baking at the last stage of proofing as it absorbs water very slowly and therefore is used to coat the bannetons.