It is with some shame that I must admit, I've never played Pathfinder before starting work on Pathfinder: Kingmaker. Still, I've been asked to talk about Pathfinder a bit at the beginning of this guide, and share some personal anecdotes, and fortunately my gaming history (some pretentious folk may call it "credentials") isn't completely devoid of merit, despite a previous lack of familiarity with Pathfinder. I have a long history with Dungeons & Dragons, and since it's impossible to talk about Pathfinder without talking about Dungeons & Dragons, it's as good a place to start as any.
While most kids my age were weaned on the Nintendo Entertainment System, I started playing video games on PC. It's a bit odd to think that my first game - at the age of four - was Pool of Radiance. I suspect most kids weren't entering DOS prompts on their dad's Tandy 1000 at that age, back when it took hours for games to install off a series of 5.25" floppy discs. I remained an avid fan of video games and Dungeons & Dragons - although increasingly rarely both at the same time - well into my teens. JRPGs ruled the market back then, and while some newer RPG franchises from the west like Diablo and Fallout were catching attention, it wasn't until late 1998 that we finally got a great RPG based off of Dungeons & Dragons: Baldur's Gate.
If you played that hallowed game and subsequently are reading this, you don't need to be told about the merits of Baldur's Gate. That the folks at Owlcat Games think highly of it is evidenced enough by its fingerprints being all over Pathfinder: Kingmaker. Sadly, while Baldur's Gate was an exemplar of a new trend in western CRPGs, it was born in turbulent times for Dungeons & Dragons. TSR (Tactical Rules Studies - founded by Dungeons & Dragons creator Gary Gygax) was purchased by Wizards of the Coast in 1997 and had been moribund since 1996. Despite this fact, TSR's logo appeared on Dungeons & Dragons products - including Baldur's Gate - until the release of 3rd Edition books in 2000. Wizards of the Coast was, in turn, purchased by Hasbro, Inc in 1999.
While it might seem extraneous, all these acquisitions and changes of brand were the wet nurses of the Pathfinder game system. After Hasbro acquired Wizards of the Coast, Lisa Stevens left the company and founded Paizo Publishing, which was founded in 2002 specifically in order to publish Dungeon, Dragon, and other magazines previously published by Wizards of the Coast. As another anecdote, when I was a kid my father purchased many issues of Dragon Magazine, presumably to enrich his Dungeons & Dragons sessions with his friends. I have many of them to do this day... although admittedly I mostly just read the comics in the back (shout out to SnarfQuest).
Paizo would also get in the business of publishing modules (called "adventure paths"), which ran from 2003-2007. In fact, Pathfinder: Kingmaker is based on a series of such "adventure packs" - the aptly named Kingmaker Adventure Pack. When Wizards of the Coast announced the imminent release of 4th Edition Dungeons & Dragons in 2007, Paizo Publishing decided to go their own way with the Pathfinder game system in order to have a live game system to support the Pathfinder Adventure Path modules. While originally based on the 3.5 Edition Dungeons & Dragons ruleset, Pathfinder - through many refinements and alterations - diverged into its own distinct game system.
Over the intervening years, Pathfinder would go on to become - temporarily at least - the world's most popular RPG system. From its humble beginning as a series of monthly adventurers, Pathfinder has grown to include twenty-four six-part Adventure Paths (both released and upcoming), a cooperative card game, a line of fantasy novels, three series of full-cast audio dramas, over fifty issues of comics and, of course, the Pathfinder: Kingmaker CRPG. With the upcoming release of Pathfinder Second Edition in August 2019, it doesn't look like the Pathfinder game system is slowing down any time soon.
-- Nathan (Haeravon) Garvin, with direction from Paizo