Pentos is based on George RR Martins westeros. It takes elements from Middle Earth. Its history is also based more on Scottish and English history, as well as Westerosi history. The lands and nature of Pentos varies massively from each kingdom.
In Pentos there are 14 kingdoms, as of now. Each kingdom is ruled from their capitol and is named after the family that run it. So for instance, the Reeds rule from Swamps Shore, so the land is known as "the land of house Reed of Swamps Shore" formally. The kingdoms are often given nicknames so keep it simple though. So "The lands of house Reed of Swamps Shore" is informally known as the Swamplands.
Pentos was until very recently ruled by the king of Pentos, the line of house Renly of Kings Keep. However a rebellion has started recently so the lands are much more decided. As of late there are two kings, King Jon Reed of Swamps Shore and king Richard Renly of Kings Keep.
1471 years ago all the dark magic was captured by the mages of Aglonby. The capture of all the dark magic in the world drove certain dark species to extinction, such as the dragon or the orc. However all the dark magic has been released back into the world by Ramsay Reed of Swamps Shore.
It is known that there is plenty of magic and visions in the world, but it is not accepted by many people in the kingdoms, mostly the commoners rather than the high lords. However a lot of the western houses look down on prophetic dreams and sorcery.
In conclusion, Pentos is not a high fantasy world, more of a low fantasy with elements from Westeros and middle Earth.