Altannia is an amalgam of high fantasy styles (ala Dragonlance/Forgotten Realms) and Steampunk (Jules Verne, Girl Genius, The League of Extraordinary Gentleman, etc). The World has recently emerged from a long dark age caused by the collapse of an over extended empire and the breakdown of trade. The central emergent power (The Alta Regency or AR), using advanced technology and magic seeks to reconstitute this ancient empire via colonialism. The regal power in Alta and it’s city states is closely tied with the Monotheistic central church of Bahamut whose ancient directives and formidable cathedral fortresses safe guarded most recorded knowledge and protected the citizenry through the dark ages. Neighboring states have been either absorbed or subjugated with three noted exceptions. To the direct south is a massive forest kingdom of Dragonkin known as The Wode, under the authoritarian rulership of a flight of ancient green dragons. The AR and The Wode recently declared cease fire on a debilitating trench war. To the west of the fire line between the two is Baan a small republic of merchants and free enterprise, similar to the circa 1800s Dutch, (this is the country of origin of the PCs). While Baan doesn’t possess the technology of the AR or the might of the Wode it is an exceptionally resourceful and nimble entity. Across the straight between the eastern and western sea lies the implanted Seelie Court. Transplanted from the feywild, this high magic kingdom of Eladrin and fey races has occupied and forced out an older kingdom of elves who have since fled north into the deep wild where they have made desperate pacts with primordial and aberrant forces in a futile effort to reclaim their lands. The Seelie court is terraforming its empire into a mirror of the feywild and the perpetual summer and spring of their pristine land stands in stark contrast to the natural environments that lie beyond their steadily growing borders. There are a few other countries and entities of note, like the monotheistic church of Bahamut, the psionic monasteries, the golem manned cloisters that withstood the dark ages among other fallen and hidden forces.
After that, take a look at your wiki. There is some more helpful info there.