Mechanically-speaking, Ratfolk in Pathfinder: Domain are identical to those found in the Pathfinder Advanced Race Guide p150. You can also find Racial Information on them on the d20pfSRD website.
Tulun Ratfolk: The extremely communal race of Ratfolk come from huge families and can be found almost anywhere in Tulun, especially since the Industrial Age. Hoarders and tinkers by nature, they love anything to do with technology and often can be found any epicenters of civilization. Another of the races who evolved from an animalistic ancestor during the Mythic Era, Ratfolk have been a constant ever since, much the like the rats they evolved from.
Place of Origin: Ratfolk originally came into existence in the areas that would later become Enotia and Rhakor, and most can now be found in Enotian lands, especially near major settlements and cities.