Normal -> Anyone can learn it. Ex - Sparks, Poison Spray, Fire bolt
Expert -> Need some investment. Ex - Fireball, Lightning bolt, Water Walk, Stoneskin
Master -> Sorcerers needs to do a promotion quest before they can learn it. Iti s the "cap" for hybrid classes like Archers. Ex - Fly, Town Portal, Meteor Shower
Grand Master -> You need to become a Lich or a Archmage. No hybrid class can reach that point. Eg - Lloyd's Beacon, Incinerate
I believe this is where Wizards of the Coast come to play ...
Since as far as i know, they litteraly demanded that game must keep DnD rules.