The window of opportunity for a Religious Victory is narrower than any of the other victory conditions, and Religious Orders will help players who are striving to achieve one before the window closes. In conjunction with Theocracy, it provides all religious units with +10 Religious Strength, which will give them a substantial advantage in Theological Combat.
Although the Buddhists (Zen, Shaolin) and Muslims (the various Sufi tariqa) have religious orders of a sort, it was Catholicism that spawned the most famous. In the Catholic Church, founding a religious order must be consecrated by the Pope … it can’t be done on a whim. The earliest that would be recognizable today was the founding of the Order of St. Augustine c. 1244 AD, cobbled together from several earlier mendicant orders of friars. By the time of the Renaissance, all sorts of holy orders were being created: Benedictines, Carmelites, Dominicans, Franciscans, Jesuits, and so forth and so on. And a number of religious orders concerned more with eliminating heathens than saving souls arose during the Crusades, such as the Knights Templar and Knights Hospitaller.