St. Dominic received his schooling in Palencia, where he spent six years studying the liberal arts, and four years studying theology. In 1191, when a famine was raging throughout the country, St. Dominic sold his precious textbooks, clothes, and furniture to help feed the hungry. "Would you have me study off these dead skins, when men are dying of hunger?" he asked his astonished friends.
In 1194, around the age of twenty-five, he joined the canons regular of in the Diocese of Osma. Canons regular were men who followed the Rule of St. Augustine and lived in community. Unlike monks, the canons were engaged in public works and ministry around the diocese.
Ten years later, when Dominic was around thirty-five, he joined the Bishop of Osma on a diplomatic mission for the King of Castile. The mission itself failed, but it brought St. Dominic to the event that would lead to the foundation of his new order.
In the South of France, Dominic and the bishop entered the Albi region of the country, where a heretical sect, the Albigensians, had taken root. (Albigensians were also called Catharists, in some places). Briefly, the Cathars believes that there was both a "good" and a "bad" God. All visible matter, including the human body, was created by the "bad" God, and thus was full of sin. Thus, even the body of Christ, the Incarnation of Jesus, was sinful in their beliefs. The "Good" God was the New Testament God, and the 'bad" God was the God of the Old Testament. Of course, this is directly opposed to the idea of one God that the Catholic Church teaches.
St. Dominic, upon meeting an innkeeper who held these beliefs, stayed up all night discussing the errors and the True Faith with him. At dawn, the innkeeper realized his error and returned to the church. St. Dominic's zeal for the salvation of souls. But as St. Dominic traveled throughout Southern France alone (the bishop having returned to Osma), he saw the devastating effects of the heresy, and knew that he had to combat it. But how?
The first people to join the order were women, who wanted to return to a strong practice of their faith. St. Dominic established a monastery for these woman at the church of St. Mary of Prouilhe. These women became the first nuns of the order.
On the night of July 22, 1206, St. Dominic saw a a globe of fire descend from the sky and and rested above the church. He saw this sign (called "Seignadou--"Sign of God") as a confirmation of his work. He would form an order of itinerant preachers who would go all over the world, combating heresy and bringing the truth of the gospel to the people. His friars would live in community, but not in monasteries, and they would devote much time to study, because in order to preach the truth, one must first know the truth. They would preach in the language of the people, so that everyone, from prince to peasant, could understand them
It took several years, but in 1214 St. Dominic established the first religious community of his new order in Toulouse. It would be governed by the Rule of St. Augustine, the same rule he'd followed as a Canon Regular, and which gave a lot of flexibility to its members. The Order was founded for two purposes: Preaching and the Salvation of Souls. This is why members of the order have O.P. after their names--it stands for Ordo Praedicatorum, "Order of Preachers."