The Lores of Magic are lists from which Wizards generate their spells. Different Wizards have access to different Lores of Magic. The eight most common lores are presented in the Reference section.
As has already been hinted at, the possible applications of magic are many and varied, leading to a potentially vast array of spells to choose from. Fortunately for our gaming convenience (to say nothing of our already tenuous sanity) very few Wizards in the Warhammer world have the gumption to harness the full spectrum of magic, and instead concentrate on mastering one or more magical disciplines, or lores.
There are many magical lores. Most represent fragments of 'pure' magic as practiced by the High Elves.
Each lore has a particular character, which is reflected by each spell within it. The Lore of Metal, for example, is grounded in alchemy, and its spells therefore act through the transmutation of one substance into another. The eight most common lores, echoing the eight disciplines that the High Elves once taught to men, are collated at the back of this book. Almost all races can use one or more of these lores, depending on the character of said race, and its magical methods. Many races also have access to their own, unique spell lores, such as the fearsomely destructive Waaagh! magic of the Orcs and Goblins. Where this is the case, the relevant Warhammer army book will contain the necessary spell list(s).