Each of the Schools of Magic refer to a different way magic is used. While other materials may have gone over the magics separately, this guide gives a brief explanation of them all in one place.
Keep in mind that each school of magic classifies how magic is used, not what type of magic is used. For example, One can use fire magic to create a fireball (evocation), or the imbue a weapon with the ability to burst into flame (enchantment), and both schools would make use of the same underlying fire magic. Elemental magic can fall into any of these categories, but most elemental spells tend to be evocation, abjuration, or conjuration spells.