From the Catechism of the Catholic Church, Simplified
The Mission of the Lay Faithful (897-899)
"Laity" are all the baptized (except for those in Holy Orders or in the religious state). By Baptism, they are incorporated into the People of God, share in Christ's office, and have their own part to play in the Church's mission, especially by directing temporal affairs according to God's will. They must bring God's enlightenment and order to society.
Their initiative is absolutely required so that the demands of the Gospel permeate temporal realities. The laity are on the front lines and must have a clear consciousness of actually being the Church (Pope Pius XII).
Right to Preach the Gospel (900)
Because of Baptism and Confirmation, they have the right and duty (individually or grouped in associations) to preach the Gospel to all. Their activity in ecclesial communities is so important that pastors cannot be fully effective without them.
Consecrating the World and the Family (901-902)
The laity are called to produce the Spirit's fruits. Their works, prayers, and apostolic undertakings (even the patient bearing of hardships) must be accomplished as spiritual sacrifices. By these holy actions the laity consecrate the world to God, offering worship by their daily holiness.
In a very special way, parents, as Christian spouses and teachers of their children, share in this work (Canon 835).
Permanent and Other Ministries (903)
Those laity with the required qualities can receive the permanent ministries of lector and acolyte. Even without these ministries, laity can fulfill certain offices (read the Word, confer Baptism, or distribute Holy Communion).
Witness of Life and Word (904-905)
Christ establishes both hierarchy and laity as witnesses. "To teach in order to lead others to faith is the task of every preacher and of each believer" (St. Thomas Aquinas).
The layperson must proclaim Christ by word and example. This witnessing has a special power in the ordinary circumstances of the world. Laypersons must seek opportunities to announce Christ to believers and non-believers.
Bringing Their Special Competence (906-907)
By special training, lay people can help in catechetics, in the sacred sciences and in the mass media. According to their special competence, lay people must make their opinions known to their pastors and even to other faithful (with due regard for the integrity of faith and for the common good).
Changing the World (908-909)
Christ gave his followers a "royal freedom" so they might overcome the reign of sin in themselves. "That man is rightly called a king who makes his own body an obedient subject" (St. Ambrose).
When the world's institutions and conditions are an inducement to sin, the laity should "unite their forces" to change them, and impregnate human works with a moral value.
Helping Their Pastors (910-911)
The laity must help their pastors by exercising various ministries or charisms for the good of the Church (Pope Paul VI). Canon law provides many opportunities for the laity to cooperate in the power of Church governance such as diocesan synods, parish finance councils, and parish pastoral councils.
Church and Society (912-913)
The faithful must distinguish between their rights and duties within the Church and within human society. They must unite the two, and be guided by a Christian conscience. Every person according to the gifts bestowed by Christ must be a living instrument of the Church's mission.