The arcane schools find mention mostly in in-game books in Dalaran. Seemingly, these schools are also referenced by characters which belong to the Kaldorei Empire, hence the most obvious inference is that they were passed down by the highborne to human mages.
I will add, however, that the eight Magic schools are overly glorified IC. It is a very flawed classification system which role-players have over-used despite its many flaws, and often it feels like it harms roleplay rather than enhance it. The amount of times I was told I “have” to be specialized in those fields and be weaker in others appears to be mostly a headcanon inference some players have made from reading two in-game books, whereas most books which feature mages (The Last Guardian, the WotA trilogy) these distinctions aren’t established at length, when and if they are mentioned. Also when we see mage training (WotA, Mage the comic) it often involves learning different schools together (ie. presence of mind and pyroblast).
While one may argue that mages specialize in many magic schools, or sub-schools, it should be reminded that almost all of this is (plausible) headcanon based off a system which Blizzard never bothered to expand or define over time after the RPG became non-canon.
Conjuration is the art of conjuring objects from thin air - therefore it ranges from summoning refreshments to summoning elemental magic (such as the iconic water elementals).
Evocation is actually mentioned as a school. Runeweaver tells us that Arcanist Doan could combine two schools, abjuration and evocation, to both defend himself and attack. The spell he uses which is classified as evocation by the writer is basically a blast wave.
As evocation it’s never mentioned again, at this stage we do not know -if- offensive spells which pertain to the elements of fire and frost would fall under the category of evocation or conjuration.
While we do not have a clear answer, this informs us that at least some magical abilities which involve harnessing magic and turning it offensive pertain to evocation, and so far the abilities mentioned by Ansirem under conjuration aren’t offensive, but pertain more to the creation of certain non-offensive objects, such as water elementals and conjure water.
If my theory is true then a pyromancer would be an evoker, not a conjurer. But again, this is mostly headcanon as we do not have evidence for or against most of these things. Heck, for all we know Ansirem’s book may actually have errors in them, and evocation doesn’t exist!
Or perhaps conjuration and evocation are the same thing, but if that’s the case it’s never stated.
Again, with all flaws of the schools I just recommend to be vague. Feel free to use them, but keep your focus on a more defined identity, imho. For example, call yourself a pyromancer, not a conjuror/evoker specialized in fire magic.
TLDR. There is seemingly some level of confusion between conjuration and evocation and this is due to the fact the definitions suck. They both exist and as far as we know either overlap a little, or they are the same thing, or offensive elemental magic is exclusive to evokers.
) as I need everything for my toon’s lore as well