The Catechism in Questions & Answers

402. What are the tasks of the Apostles in the church of Christ?

Jesus Christ rules His church. To this end He makes use of the Apostles. The Apostle ministry is the original ministry of the church. It is the only ministry given by Jesus Himself. The most important tasks of the Apostles include the proclamation of the gospel throughout the world, the proclamation of the forgiveness of sins, the dispensation of the sacraments for the living and the dead, and the ordination of ministers. So it is that the bridal congregation is gathered and prepared for the return of Christ through the activity of the Apostles.

Apostolate: see Questions 413., 424. et seq., 433. et seq., 453. et seq.