Larian Studios Forums Baldur's Gate III Baldur's Gate III - General Spells: who can learn what ?

To answer the OP's question a little more fully, there are eight different schools of magic and all spells fall into one of them. Each of the schools has a general focus:
Evocation - direct damage
Abjuration - protection
Conjuration - creating objects and creatures; also, teleportation
Illusion - creating illusions
Enchantment - charming and beguiling creatures
Transmutation - changing things into other things; other effects related to form
Divination - learning things and improving senses
Necromancy - manipulation of life force (including healing)

In addition to belonging to a school, every spell is on the spell list for one or more classes or subclasses - meaning characters with appropriate levels in those classes can learn that spell. Different classes might have different sources of power (i.e. clerics/paladins call on their deity, rangers/druids draw power from nature, wizards learn to control magic through study, warlocks are granted magical power by a patron, sorcerers basically win the lottery, artificers build devices), so the underlying mechanics of how a spell is cast might be different, but the game mechanics are more or less the same (e.g. if a ranger and a sorcerer cast Absorb Elements, the effect is identical).

Most classes don't care about what school a particular spell belongs to. Wizards do, because most wizard subclasses focus on a particular school and give them benefits for casting those spells. There are subclasses that care about magic schools; e.g. Arcane Tricksters focus on Enchantment and Illusion while Eldritch Knights focus on Evocation and Abjuration.

All of the above is how the 5e rules work. BG3 is somewhat based on this, but there are a few changes. The most notable changes are related to spell scrolls, which deviate from the 5e rules in two big ways:
1) In 5e, you can only attempt to cast a spell from a scroll if that spell is on your class' spell list (with a couple of exceptions that aren't critical to this explanation). And if a spell is on your class' spell list, but it's level is higher than you can normally cast, there's a chance for you to fail and waste the scroll. So, a wizard can cast fireball from a scroll, but a paladin can't, because fireball isn't on the paladin spell list. In BG3, any character can cast any spell from a scroll; class and level don't matter at all.

2) In 5e, wizards get to add two spells to their spellbook every time they level up. They can also copy spells into their spellbook from scrolls, provided the spell on the scroll is one that they would normally be able to learn (i.e. it's on the wizard spell list). In BG3, they can copy any spell from a scroll; so wizards can learn to cast Cure Wounds and other spells that they have no business knowing.

And yes, this game does a pretty bad job of teaching players how to play it. It would benefit quite a lot from both tutorials and access to reference materials.