Faith and religion are complicated subjects. On Golarion there is manifest verifiable proof of the existence of beings capable of altering reality who call themselves gods. This effect ripples out across the mortals inhabiting that world, shaping cultures and causing epic dramas to unfold under the influence of competing divine forces.
There are creation myths, moral tales and great battles of good and evil. On Golarion good and evil are more than an idea. Law and chaos define more than social relationships or ethics. Holy water will burn demons or vampires. Wounds will close before your eyes. Curses can literally immediately kill you. While remote a god could literally smite someone with lightning. What is a player supposed to choose for their character? How does a player represent their character dutifully in such a world?
The lore in Pathfinder does a fair job in representing many faith archetypes, often loosely based on Earth’s believe systems, and then gives them a deity or structure for players to choose what they feel comfortable playing and what best fits their characters. The team has gone to great lengths to try and be fair and welcoming as well as represent as many possibilities as they can while keeping the fictional world distinct.
Choosing a deity becomes a balance between mechanical game benefits for some class builds like clerics and champions as well as a representation of character identity. This aspect of the game is relatively easy to deal with. Clerics and champions will use the charts in the core rule book or supplement books to choose abilities that they need, and which fit their characters. Other classes will read through the deity profiles and find one that either aligns with themselves or with their character.
Where matters get complicated is when plots and stories begin to delve into the drama of how faiths interact with each other and the world. Each person at the table approaches scenarios from a specific bias unique to them which is used as a filter while they interpret mechanical concepts like good/evil or law/chaos into narrative constructs of storytelling. The common result is conflict when players are confronted with moral or ethical quandaries where they as the person may be at odds with their fictional character. That is also where the fun is.
Every table can become a place to explore with friends the moral and ethical dilemmas that arise from unique situations. Is working with a devil worse than bowing to an evil god? Will you break the nation’s law to help an angelic servitor? Should you murder one villain to save the lives of thousands? Will risking redemption of the villain be accepted by the nation they hurt? Can someone unquestionably evil have reason to perform observably good acts?
Does a follower of Torag honor the people of his deity above all others? Can the paladin of Iomedae put aside her differences with the Hellknights to save the village from a horde of undead? The GM’s role in this arena is fluid. They present the scenarios and reactions to the choices of the players allowing large control on the depth of complexity any given situation evolves to. Sometimes a scene touches a player so deeply the GM must be aware of when to back off and allow time to process. Sometimes what seems should be a deep emotional quandary is neglected entirely, consequences be damned. If your table signed up to kill bad guys and save damsels in distress, they may not want to deal with morally grey villains or role reversed damsels. There is no handy chart available for what level of cognitive ambiguity players might be ready for.