Catechism of the Catholic Church §1043 — excerpt
Sacred Scripture calls this mysterious renewal, which will transform humanity and the world, "new heavens and a new earth." It will be the definitive realization of God's plan to bring under a single head "all things in [Christ], things in heaven and things on earth."
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.