1 Kyros: The Golden Citadel, then. This will be tricky.
2 Kyros: Making the waters reveal the way is a combination of Alteration, Evocation, and Divination.
3 Mordekai: Different branches of magic? Do you do them all?
4 Kyros: No. I wouldn't be caught dead doing Necromancy.

The original edition Advanced Dungeons & Dragons rules classified spells by types like this. There were, from memory:

• Abjuration
• Alteration
• Conjuration/Summoning
• Enchantment/Charm
• Evocation
• Divination
• Illusion/Phantasm
• Necromantic

While some of these words were clear enough in meaning, others ("abjuration") were classic Gygaxian terms that sounded cool but none of us in my playing group actually understood what they meant. Do you know why?

Despite these cool-sounding words being attached to every spell in an apparently systematic and meaningful way, the rules made no mention of them anywhere else. There were no spells that protected you from Alterations, for example. No magic talismans that stopped anyone from using Necromantic magic on you. No items that boosted your powers of Evocation. There were no magic users who specialised in Enchantment/Charm spells. No nothing that referred to any of these types.

There were illusionists, as a subclass of magic users, and they kind of specialised in illusions, but not simply by having a bonus to learn or cast illusions as you might expect, but by having a completely separate spell list that emphasised illusions, although not exclusively. In hindsight, it was a really strange way to organise the rules to allow one particular type of magical specialist, while not providing any support for characters that might bedescribed as enchanters, or diviners, or necromancers.

It would have been better to have a single big list of spells, and then some mechanic to let wizards choose to specialise in some of the branches of magic at the cost of being weaker in others. In 2nd and 3rd edition Dungeons & Dragons they actually did this, calling them schools of magic. But for us tyros stuck in the 1980s with the first edition, this remained an elusive thing of the unforeseeable future, and the spell types were simply another byzantine piece of the game system that seemed to serve no purpose but to sound cool.

(Apparently the schools are gone again in 4th edition, but I haven't kept up to date so can't explain what, if anything, their effects have been replaced by.)