Spells fall into two main categories: wizardry spells and prayers. Casting wizardry spells requires spell points and the applicable skill for each spell. Casting prayers requires grace from a god and the praying skill. Most spells also belong to a Path; and players may be attuned, repelled, or denied a particular path by their race, class, or god.
Spell details and more information about the skills needed are at the following links.