Schools of Magic

There are eight Schools of Magic, each focusing on a different area of The Weave.
Each school has both two schools with which it is compliementary and two schools with which it shares very little. Magicians of similar schools tend to have more in common, and perhaps greater tendencies towards collaboration, than magicians of disparate schools.

None of this really matters. All that matters is your ability to craft the Weave to your bidding. All else is claptrap, not power. And why else are you doing magic?

— Loikiel

Abjuration

The School of Abjuration focuses on magic dealing with protection, especially through the removal or blocking of harm. Example spells include Alarm, Arcane Lock,
Complementary Schools: Illusion & Necromancy.
Disparate Schools: Evocation & Enchantment

Conjuration

The School of Conjuration focuses on the creation and/or displacement of material objects and beings. Example spells include Entangle, Teleport, Plane Shift, Wish.
Complementary Schools: Necromancy & Enchantment.
Disparate Schools: Illusion & Transmutation

Divination

The School of Divination focuses on revealing information and acts of communication. Divination is really its own thing, and is (to its practitioners) the central facility of all magic. To other magicians, it's often seen as a somewhat trivial school, highly practical, for sure, but not truly engaged in the deep secrets of The Weave. Example spells include Identify, Scrying, Foresight.

Enchantment

The School of Enchantment focuses on influencing creatures to act in ways consistent with the magician's will. Example spells include Charm Person, Zone of Truth, Power Word Kill.
Complementary Schools: Conjuration & Evocation.
Disparate Schools: Illusion & Abjuration

Evocation

The School of Evocation focuses on manipulating The Weave to cause material--and usually damaging--effets in the world. Example spells include Magic Missle, Spiritual Weapon, Fireball,Meteor Swarm.
Complementary Schools: Transmutation & Enchantment.
Disparate Schools: Abjuration & Necromancy

Illusion

The School of Illusion focuses on magic that decieves the senses. Example spells include Disguise Self, Invisibility, Simulacrum, Weird.
Complementary Schools: Abjuration & Transmutation.
Disparate Schools: Enchantment & Conjuration

Necromancy

The School of Necormancy focuses on magic that manipulates the vital life force, both in its existence and its absence. Example spells include Spare the Dying, False Life, Blight, Resurrection.
Complementary Schools: Abjuration & Conjuration.
Disparate Schools: Evocation & Transmutation

Transmutation

The School of Transmutation aims to transform physical states. Example spells include Feather Fall, Stone Shape, Polymorph.
Complementary Schools: Evocation & Illusion.
Disparate Schools: Necromancy & Conjuration

The relationships between the Schools is quite subtle, and only after years of study can it be expected they are fully understood. But you will gain much nuance and refinement from the journey, and your magic will reach levels of subtlety heretofore unknown.
Why is Power Word Kill Enchantment and not Necromancy? The answer explains the inner workings of the spell. What is the difference between a disguise and altering someone's true form? It's the difference between Illusion and Transmutation.

— Guattari