Ispar is the name of the world where humans (among other species) originate from. Humans from Ispar are known as Isparians. The four human cultures (Aluvian, Gharu'ndim, Sho, and Viamontian) currently inhabiting Dereth are all Isparians.
Ispar as a whole can be compared to the ancient and medieval western world. The map of Ispar has similarities to Europe, the middle east, and parts of Asia, all combined together around a sea similar to the Mediterranean sea.
For information on the real world basis for the various Isparian people, visit their culture's page.