Jani Vesperian worlds are a subtype of Vesperian worlds. They are tidally locked, with a stable biome along the terminator line. Towards the day side, the landscape becomes scorched desert, and towards the night side it becomes tundra and arctic conditions.
Such worlds will often have a low level of surface water, generally less than 30%, and an atmosphere thinner than standard (though thick enough to allow surface water and life). This leads to poor distribution of heat across the world's surface, and quite a thin 'terminator' zone where the climate is reasonable for life.
It's possible for rivers, sometimes whole seas, to flow round to the day side and boil off as the temperature rises.