Drap plat and Drap house

In contemplating buying sheets in France, it is not simple or easy. Measurements are not standard, and are nothing like the US single, full, queen king that we find in any store that sells sheets. First one must discern whether we are looking at flat or fitted sheets. Apparently a fitted sheet is "drap house" which appears to match the actual measurements of the bed. A flat sheet is "drap plat" which has larger measurements as the length and width are larger than the actual bed measurements. All quite intimidating and confusing, but we figured it out with some assistance from a French women who admitted even she finds it confusing.