§1. In the Church there are associations distinct from institutes of consecrated life and societies of apostolic life; in these associations the Christian faithful, whether clerics, lay persons, or clerics and lay persons together, strive in a common endeavor to foster a more perfect life, to promote public worship or Christian doctrine, or to exercise other works of the apostolate such as initiatives of evangelization, works of piety or charity, and those which animate the temporal order with a Christian spirit.
§2. The Christian faithful are to join especially those associations which competent ecclesiastical authority has erected, praised, or commended.
Source: Code of Canon Law (Vatican.va)