Catechism of the Catholic Church §570 — excerpt
Jesus' entry into Jerusalem manifests the coming of the kingdom that the Messiah-King, welcomed into his city by children and the humble of heart, is going to accomplish by the Passover of his Death and Resurrection.
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.