Assumption
The dogma states that "Mary, Immaculate Mother of God ever Virgin, after finishing the course of her life on earth, was taken up in body and soul to heavenly glory." Some distinctions: We don't know if she died first and then was assumed, or if she was assumed on the verge of death, or if she was assumed before dying. Also, we distinguish her assumption from the ascension of Jesus: Jesus ascended to heaven under his own power and on his own authority; Mary was assumed into heaven by the grace and power of God. It is symbolic of God's hope that all of us will one day be in heaven - that we will make the journey to our true home and bask in God's presence.
Regarding her bodily assumption, we believe that at the end of her life, due to her special place as the mother of Jesus, God lifted her (assumed her) directly into heaven (body, mind, soul & spirit). As the "first fruits" of Christ's redemptive sacrifice, she was able to forego the corruption of the physical body here on earth and proceed directly to the glory of the resurrection.
Perpetual Virginity
The earliest extant manuscript which talks about Mary's perpetual virginity (no sexual intercourse, no further children) is the Protogospel of James from around 150 AD. We see further discussion and development and finally acceptance of this teaching around the middle of the 4th century. Origen, Basil, Ambrose, Jerome & Augustine all defended the doctrine, which was solemnly taught in 553 at the 5th Ecumenical Council held in Constantinople. Like the doctrine of divine motherhood, Mary's perpetual virginity points to the singular nature of her son, Jesus - it is not a detraction from the normal way of life for spouses, it is not a condemnation of married sexual love, and it is not an exaltation of celibacy over sexuality: it is another Marian teaching subsumed under Christology because it helps focus on the unique nature of the incarnation of Jesus.
I’m aware of the texts in the Gospels that talk about the brothers and sisters of Jesus. The word that's usually translated as "brothers" (or “brothers and sisters”) in the NT can also refer to cousins, young uncles, close family friends, etc. - more of a close-knit tribe/family than just biological siblings. Since the word can go either way, and since the Church has defined the perpetual virginity of Mary (going along with the teaching of the early church) we take it to mean that Mary was indeed ever virgin.
Having said all that, we do not worship Mary, nor pray to her statues, nor offer offerings to her in lieu of God . . . all of the honor given to Mary as the Mother of Jesus and the Mother of God flows exactly from her special, singular and unique relationship to her son: one part of the Holy & Blessed Trinity.
Queen of Heaven (Not a dogma, but it fits well in this section)
Regarding Mary as Queen of Heaven, in ancient Israel it was the king's mother who reigned as queen, not his wife. Most kings had harems full of wives and concubines - none of them were ever called "queen" - it was always the mother of the king (and there was only ever one mother!) who was given that title in relation to her son. In 1 & 2 Kings the name of the Queen Mother is mentioned many times along that of her royal son. In Jeremiah 13:18 the Queen Mother is shown as wearing a crown just like her son the King. The Queen Mother was expected to help her son in his work, and she often served as an advocate for the people, hearing their petitions and taking them to the king. In 1 Kings 2 we have an account of Bathsheba coming in to see her son, the king - she is treated royally, with the king bowing to her and seating her in a place of honor - he listens to her and faithfully follows her wishes.
This is the historical and scriptural background which underscores the Catholic and Orthodox veneration of Mary as Queen of Heaven and Earth. For the ancient Jews who saw Jesus as a new Davidic king, Mary would naturally inherit the role of Queen Mother. When Elizabeth greeted Mary she used courtly language: “how is it that the mother of my Lord should come to me." In the courtly language of the time "my Lord" was another way of saying "my king" - from the beginning of the gospel accounts we are given hints as to how Mary was regarded by those around her.
Continued in two days :)
Blessings & Peace,
Hugo