Catechism of the Catholic Church §1135 — excerpt
The catechesis of the liturgy entails first of all an understanding of the sacramental economy (Chapter One). In this light, the innovation of its celebration is revealed.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.