What is pre congregation canonization?

Today, all causes for sainthood must be investigated by the Sacred Congregation for the Causes of Saints in the Vatican. They may recommend to the pope that a case be approved for sainthood. The pope, alone, then makes the decision. Prior to the existence of the Sacred Congregation any bishop could declare a saint, usually at the urging of a parish, diocese or religious order. This came to an end in the 12th century. Those declared a saint in these early years are called precongregational saints