Soya flour is a golden-coloured flour that is high in protein (typically around 40%). Being gluten-free, it does not bind, so is usually added to wheat flour in order to make bread. This adds taste to the bread, as well as increasing the protein content. Soya flour tastes a little bit like chickpea flour ("gram flour").
You can also use soya flour together with wholemeal flour, in order to make tasty nutritious chapatis.