This is the pathfinder system, like pen and paper pathfinder. The stats, spells, classes, feats, monsters, rules etc are all from the pathfinder ruleset. The game is the equivalent of a computer being a digital DM and running you through the "kingmaker" pathfinder campaign; a campaign where you fight monsters and bandits while turning your backwater barony into a ripe and fruitful kingdom. The game takes place on Golarion(yes established; yes pathfinder). This setting includes the connected worlds/planes, deities and lore of pathfinder: but the game if kind enough to contain most of the pertinent information. While the setting is pretty huge it's not a huge worry... as with most campaigns it's localized in a certain area in the universe/setting(which is usually a global or contenental scale affair), so you mostly play within your kingdom and the surrounding areas

Most pathfinder core races would be pretty familiar to tolken level fantasy; think human, elf, gnome, dwarf, halfling, half orc... the two humanoid races in game that wouldn't compute 100% are easy enough to explain: aasimar(half celestial/'angel'), and the dlc race; tiefling(half demon/ demonblooded), but those two are from the diverse but less populace but still playable, "standard races"... you'd still have to look at what specific bonuses and atributes each race has to offer for creating your main character... As far as monsters go, there's a bestiary, but its mostly standard stuff; goblin, orcs, trolls, bandit, wyvern, wolf, worg, werewolf, hydras, dragons, owl bears, etc... There's some D&D/pathfinder stuff like a gnoll (dog headed humanoid, kind of pack mentality)... There's also a dictionary for stuff like vocab, ie: what does "masterwork" mean and how does it compare to "+1" (answer: masterwork is +1 to the d20 roll for 'accuracy', or the roll "to hit", whereas a +1 magic weapon would give you +1 to hit AND +1 damage). Same goes for the deities and such, if there's something thats highlighted in dialogue and/or theres some fantasy vocab you don't understand, it's probably described in a note somewhere, it's fairly basic but you'd use it to sus out things like: deities like serenrae and erastil are ones you hear of but shouldn't fear as their good, whereas maybe someone like lamashtu might be more culty or worrisome... You can mostly use context but the information is there... Not to mention google/wiki

There are some differences from paper if your familiar with it but nothing major, mostly cutting out feats/abilities that wouldn't make sence or be possible within the limitations of the computer based system. Stuff that would either break the game or the game engine because a PnP campaign can have unlimited artistic freedoms and liberties taken as it's entirely made up between the dm and players so the base ruleset had a lot of stuff that allows for doing beyond videogames or prewritten campaigns being 100% scripted, in this case by the computer/developers (just read like 5 r/dndgreentext posts and you'll know what im talking about). They don't cut anything too jarring even for those familiar with the system, but it is technically not the "full system" if you were unsure or curious about that. It's very close in game but it's immediately noticible in character creation because at least one race and class in the game are dlc, and that's not mentioning, while there are a few non core-race races (aasimar and tiefling), they are missing the other (18!) pathfinder standard races...