The lay faithful are those Christians who are incorporated into Christ and the Church by Baptism and who, unlike priests and religious, are called to live their share in the priestly, prophetic and kingly office of Christ in the secular sphere.
By the secular sphere is meant the earthy realities in which the lay faithful live and work. It is the world of the family, the place of work and recreation, science and technology, the arts and professions, politics and government, the mass media and recreation, national and international relations.
"The laity must take on the renewal of the temporal order as their own special obligation" (Apost. Actuositatem, 7). It is this activity, this vocation that distinguishes them from the priests and the consecrated people.
The identity of the lay faithful is born in and nourished by the Sacraments of Baptism, Confirmation and the Holy Eucharist. For the married, it is further specified and fortified by Matrimony.