Catechism of the Catholic Church §2679 — excerpt
Mary is the perfect Orans (prayer), a figure of the Church. When we pray to her, we are adhering with her to the plan of the Father, who sends his Son to save all men.
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.
Also cites: LG 68-69