Rice flour is a white (or brown) flour milled from regular (not glutinous) rice used in Asian cooking for making cakes and desserts. Until the gluten-free movement you would typically find rice flour in most Thai, Vietnamese or other Asian markets. However now it's available through many main stream brands such as Bob's Red Mill.
Glutinous rice flour is an entirely different product so don't confuse the two.
If you need an alternative to rice flour you can substitute:
As a thickener substitute: