In this master thesis, we will discuss the role of lay believers in the teaching ministry of the Church. Christ entrusted the deposit of faith to the Church to sacredly guard, further explore, proclaim, and interpret the revealed truth (cf. Canon 747). Its primary task is teaching, as mentioned in Book III of the Code of Canon Law. Thanks to the Second Vatican Council, the Church began to reflect on itself as a community. One of the most important documents of that council is Lumen gentium, which speaks clearly and comprehensively about the dignity and tasks of the laity in God's plan of salvation. The Holy Spirit bestows special gifts and charisms to the faithful, and they have the right and duty to use them in the Church and the world for the good of humanity and the building up of the Church (cf. AA 3). The goals of the apostolate are evangelization, sanctification, and charitable activities (cf. AA 6-8). In their formation, the laity should fulfill the mission of Christ and the Church by living their faith. We will conclude the paper by discussing the right of believers to associate and citing the positions of documents from the Second Vatican Council and the Code of Canon Law. The Council emphasizes that humans are social beings, and this collaborative apostolate is a sign of the communion and unity of the Church in Christ. Through baptism, believers are united to Christ and are called, according to their state in life, to fulfill the mission entrusted to them by God.