A biogeographical realm is the largest biogeographical division. It is a continent or continent-sized area with unifying features of geography and fauna/flora/vegetation. This rank more or less corresponds, in other classification systems, to the "kingdom" of the florist and the "region" of the faunist.
The system of biogeographic realms (or regions) integrates information on the (1) distribution of species and (2) distribution of ecosystem units. Each biogeographic region is subdivided into a subset of biogeographical provinces. Each province is characterized by a dominant ecosystem (also called a major biome or biome-complex). Provincial boundaries can subdivide the area of a biome where significant faunal or floral differences occur. Also large areas of relatively uniform faunas and/or floras are subdivided on the basis of changes in the structure of vegetation.