Flour is a powder, made by grinding wheat grains.  "Soft" or "weak" flour means the gluten content is low, "hard" or "strong" flour means the gluten content is high.

Whole Wheat vs. White

Wheat's seed is made from three portions - the germ, the bran and the endosperm. White flour has been stripped of the bran and germ leaving behind the pale endosperm.  It has longer shelf life than whole wheat flour. It has milder flavour and less fibber and protein. Whole wheat flour is made from grinding every 3 parts of the wheat seed.