Flour is the milled powder of grain. The source grain can be wheat, barley, oats, rice or rye. Other flours can be made from potato, peas and other seed based sources. The quality of the flour depends upon the milling size and whether it is sieved or not.
Wholemeal flour is the whole grain, including the husk (bran). the milling quality is what is generally called type 2 flour. If the flour is sieved, the husk is removed and the remaining flour is called white flour or type 1 flour. Milling finer will give type 0 flour.
Pasta flour is milled to a much finer gauge and is referred to as type 00 flour. This gives a much more pliable dough which can be worked into fine sheets without tearing.. 00 flour is always sieved into white flour.
Wheat grain contains gluten. There are two types of gluten molecule - glutenin which gives the dough strength and glandin which gives the dough elasticity. Insoluble forms of albumin in grain form the gluten molecules and the albumin content of wheat grain is generally around 12%.
Wholewheat flours contain about 10% gluten, strong white flours have around 14% gluten and 00 pasta flour has usually 7% gluten. Pastry flours also have a lower gluten content that wholemeal flour. The higher gluten flours will result in a better rise in the dough.