The original ark of the covenant was a box made from precious wood and lots of gold, the absolute best and purest materials. The “glory” of God overshadowed it when God spoke to the Jews. Inside it, the Jews kept the tablets with the 10 commandments (The Law), the staff of Aaron representing the High Priest, and the manna (bread from Heaven) which sustained them during the exodus in the desert.
Mary held in her womb Jesus - the incarnation of The Law, the new High Priest, and the new Bread from Heaven (and the new Glory of Israel). Hence, Mary is the new Ark of the Covenant. This is directly referred to in the last sentence of Revelation 11 and the first sentence of Revelation 12.
There’s lots more but this is off the top of my head
DISCLAIMER: Catholic Answers has turned over the archive to Catholic-Questions.org and no longer owns, manages, or moderates the forums. For additional apologetics resources please visit www.catholic.com.