Every map in Empires of Sorcery consists of a number of different terrain tiles. Each terrain type has unique bonuses that affect some aspect of city management. Certain races also receive distinct race-specific bonuses from particular terrain types.
Essentially, each race will have one or more "home terrains." Home terrain is easy to move through and find food in, so it affects movement cost and city management differently for the "home" race than for other races.