Depending on the grind (grinding action), you get a semolina so-called upper: only the central part of the kernel of the wheat kernel has been milled or common because it contains more parts peripheral to the grain.
During its transformation, the semolina which is then a paste is cut into small pieces of different sizes and then sieved. Depending on the size of the grains, there are: semolina big, used for the couscous, the semolina medium which is used both in cooking and pastry. The semolina fine as to it allows the manufacture of pasta and serves as a binder in pastry and finally the very fine is mostly consumed by babies in their porridge.