There are four types of flour, as
defined by the rate of mineral or ash: the materials or
impurities from the grains of wheat.
The type of flour is defined by zeros of 1-4: 0000 flour
is the finest and whitest.
The 000 for making bread because of its high protein
content allows the formation of gluten and get the
pieces keep their shape.
The 0000 is more refined and more white, having a low
gluten formation is not a good gas container and the
bread lose shape. Therefore only used for sliced bread
in pastries, cakes, etc.