Basic: A basic spell is the easiest to learn and to teach. Basic spells often require no components and can easily be learned by anyone although NPC teachers will usually charge money or components to teach these spells.
Complex: Complex spells are more difficult to learn and teach, requiring a greater amount of effort on the teacher and the students part in learning. NPC teachers will charge more money or components that with a Basic Spell.
Erudite: Erudite spells are very difficult to learn and teach, such that teachers will often place restrictions or errands upon those who they wish to teach these skills. An NPC teacher will only part with an Erudite spell if he is done a great favor by his would-be students.