Some spells (or even entire spell schools) have been hidden or lost through the ages. Whether they are too dangerous or for other reasons, adventurers can sometimes stumble upon new spells (or wrench them out of the undead hands of a defeated Lich).
Secret Spells
Core Rules v2 p. 45
Related Rules
2Range and ReachMagic / Targets, Areas & Saves
Range & ReachAdventuring / Movement, Range & Space