The Delhi Sultanate represents a prime example of an Islamic state on the outside of the Caliphate system. Essentially, a Sultanate (ruled by a sultan) is a place where the Sultan claims to rule the territory, but not the Islamic Faith (think of Kings vs. Popes in Europe). The Delhi Sultanate is actually 5 different kingdoms. However, it does carry some weight in AP World History as they came into contact with some of India's greatest invaders (Mongols, Tamerlane, Mughals).