Official Catholic doctrine on Mary is called Mariology; some significant roles she plays include:
Mother of God: Mary gave birth to the Son of God, so although she was human and could not create God, she gave birth to Jesus, who is God, which makes her the Mother of God.
Mother of the Church: This title can only be properly understood as a metaphor: Christians are children of God and brothers and sisters in Christ by adoption. So by extension, Christians inherit Christ’s mother Mary.
Mother of the Mystical Body of Christ: Mary is called the Mother of the Church, because she’s the Mother of Christ, and the Church is the Mystical Body of Christ. So the Mother of Christ can also be called the Mother of his Mystical Body. This mystical title means that the Church is more than an external organization, structure, and institution, but also and more primarily, it’s a union of all the members forming one body.
Mary is the only person beside Jesus who was bodily assumed into heaven — the Feast of the Assumption (Assumption Day) is celebrated on August 15 every year. She has also appeared in visions more often than any other saint.