Q. 1. What does the "Assumption of Mary" means?
A. 1. By Papal Proclamation. "Munificentissimus Deus," on November 1, 1950, Pope Pius XII declared infallibly that the Assumption of the Blessed Virgin Mary was a dogma of the Catholic Faith.
Likewise, the Second Vatican Council taught in the Dogmatic Constitution Lumen Gentium that "the Immaculate Virgin, preserved free from all stain of original sin, was taken up body and soul into heavenly glory, when her earthly life was over, and exalted by the Lord as Queen over all things (n. 59)."
Therefore, it can be said that the Assumption of Mary is a reference to her being taken to Heaven at the end of her earthly life.
Further details can be found in the Catholic Encyclopedia