§1. The Church fulfills its sanctifying function in a particular way through the sacred liturgy, which is an exercise of the priestly function of Jesus Christ. In the sacred liturgy the sanctification of humanity is signified through sensible signs and effected in a manner proper to each sign. In the sacred liturgy, the whole public worship of God is carried out by the Head and members of the mystical Body of Jesus Christ.
§2. Such worship takes place when it is carried out in the name of the Church by persons legitimately designated and through acts approved by the authority of the Church.
Source: Code of Canon Law (Vatican.va)