The campaign is titled "Ancient Thrones, Fallen Kings" (which is a somewhat cryptic title, but the meaning will become clear in time). It is a mixture of a "sandbox" campaign with major narrative elements. In other words, there are major plot arcs but at the same time players should feel free to push the story in directions that fit with their characters' histories and motivations.
The campaign takes place in the world of Mythosa, naturally. Complete familiarity with the setting isn't necessary, but you should at least review the Six Things to Know about Mythosa to get a basic idea of what's going on. The campaign is/has been a mixture of city, wilderness, and dungeon adventures.
The campaign uses Pathfinder, with little in the way of house rules (see the mechanics section below for deviations from the standard rules). While the campaign is fairly liberal with what is allowed from the various rulebooks and supplements, the DM naturally reserves the right to alter or prohibit any of the rules or game elements at any time.
For further information, see the Pathfinder Guidelines.