What magic is
Not every hero casts spells, but the ones who do reshape what a party can attempt. Magic in Pathfinder comes from four traditions — arcane, divine, occult, and primal — and your class decides which one you draw on. A wizard's power is arcane and studied; a cleric's is divine and granted; a bard's is occult and performed; a druid's is primal and wild.
The tradition colors what your spells can do, but the machinery underneath is the same across all of them. Learn it once and you can read any caster's sheet.
Ranks and slots
Spells come in ranks, 1 through 10, and the higher the rank the stronger the spell. You cast from a set of daily slots — a handful at each rank you've unlocked — and casting a spell spends a slot of its rank. When they're gone for the day, a night's rest brings them back.
How you fill those slots depends on your class. A prepared caster (like a wizard or cleric) chooses each morning which spells go into which slots, tailoring the day's loadout to what's ahead. A spontaneous caster (like a sorcerer or bard) knows a smaller list but casts any of it freely, spending a slot on whatever the moment calls for.
Either way you can heighten a spell — cast it using a higher-rank slot to make it hit harder or reach further. Many spells are written to scale, and a prepared caster can slot a low-rank spell into a high-rank slot to get the bigger version.
Casting a spell
Casting takes actions like anything else — most spells cost two of your three, some one, a few three. That action cost already folds in the words, gestures, and materials a spell needs; you don't track those separately here.
What a spell does when it lands depends on how it's aimed. Some make a spell attack against a target's AC, hitting and critting just like a weapon. Many instead force a saving throw — the target rolls to resist against your spell DC, and the four degrees of success decide how much of the effect sticks. Others simply happen: a buff on an ally, a light in the dark, a wall of stone.
Both numbers come from the same place: your spell DC is 10 + your spellcasting proficiency + your key attribute modifier, and your spell attack is that same proficiency plus your key modifier. So the attribute that defines your class — a wizard's Intelligence, a cleric's Wisdom — is exactly what makes your magic land.
Cantrips and focus spells
Two kinds of magic don't spend your daily slots.
are the spells you can cast at will, as often as you like. They never run out, and they automatically scale with you — a cantrip is always heightened to a rank equal to half your level rounded up, so your reliable standby keeps pace as you grow instead of falling behind.
are the signature magic tied to a class feature or a feat — a cleric's domain power, a druid's order spell, a sorcerer's bloodline magic. They draw on a small pool of instead of slots, and like cantrips they're always cast at your highest rank. Spend a point to cast one; recover one by spending ten minutes to between fights. The pool holds one to three points — small on purpose, which is what keeps these spells special.
Rituals
Beyond the spells a caster slings mid-adventure, there are — long, deliberate magic that anyone can attempt with the right skills, not just spellcasters. A ritual takes time and often a group, and it reaches for effects too large for a single slot: binding a spirit, raising the dead, sealing a gate.
Rituals rarely come up in a fight. They're the tool for the problem a battle can't solve, and a good one can turn a whole campaign.