Unbleached and bleached. Unbleached simply means that the flour has not undergone the process of bleaching and hence will not have the pure white color. Chemical bleaching/whitening agents or atmospheric oxygen is used to bleach all purpose flour and hence such flour is also called refined flour. Maida, cake flour are examples of bleached flour.
Enriched flour is all purpose flour which is enriched with some of the nutrients which are lost during the process of milling the flour. In US and Canada it is mandatory to fortify the white flour with thiamine, riboflavin, niacin, folic acid and iron in the amounts required by the regulations of the respective Governments. It’s important to note that even though all purpose flour is enriched it does not have all the nutritional benefits of whole wheat flour.