How do knights of the order differ from ordinary knights?

The knights who were members of the spiritual knightly orders led an ascetic life. They prayed a lot, observed all the fasts, they were forbidden to do many things (for example, to marry). For disobedience, the knight-monks were severely punished by their commanders. Knight-monks helped pilgrims and those in need, guarded them, and also fought with Muslims (Moors and Saracens), pagans and other Christians (by order of the Pope). Their activities were in the interests of the order.

Ordinary knights could enter the service of any lord, they were not bound by strict vows.