The lay apostolate is made up from laypeople and consecrated religious who exercise a ministry in cooperation with the Catholic Church. These organizations cooperate with ecclesiastical authorities. They operate "under direction of her pastors" but are not members of the official Church hierarchy nor in Holy Orders. Apostolates operate with the permission of the local Ordinary of a Diocese, but often without material support.
This is a special case of a normal Catholic lay organization; usually these organizations obtain permission from the Church hierarchy, and operate in cooperation with the Church. In many cases, where the Priests are unable to function in specialized situations, like dealing with computer technology, medical care, or broadcast equipment, a lay apostolate may be formed to provide those specialized technical skills.
Apostolicam Actuositatem is the Second Vatican Council's Decree on the Apostolate of the Laity. It defines the mission of the lay Christian faithful to both "lead non-believers to the faith and to instruct, strengthen, and encourage the faithful to a more fervent life".
Certain lay groups that were created in the years following the Council have advocated a series of dissident positions and have turned into activist groups within the Church. Call to Action (CTA) is an organization that advocates for a variety of causes within the Roman Catholic Church. Call to Action's goals include women's ordination, an end to mandatory priestly celibacy, a change in the church's teaching on a variety of sexual matters, and a change to the way the church is governed. Another controversial lay group was Le Sillon by Marc Sangnier, which was condemned by Pope Pius X at the beginning of the 20th century.