While always a human being like the rest of us, Mary is also strikingly different from all of us. The difference in Mary, of course, derives from God. The early Church soon realized that Mary, as mother of Jesus, was not just the mother of his physical human body but is correctly and necessarily called Mother of God.
Thus, Mary has a very special relationship with the Trinity: chosen by the Trinity, Mary conceived Jesus by the power of the Holy Spirit. Jesus was "one sent by the Father." Hence, as Jesus' Mother on earth, Mary has a very special relationship with God the Father. Reflection on this great mystery of Mary led the Church to declare that Mary was conceived without original sin and that she was assumed into heaven.
Like her Son, and like the rest of us, Mary had to face death. She did not rise from the dead in the same manner of Jesus. Yet by her special relationship with Jesus, she received the grace of the resurrection in a special way, a way more fitting to her reality. This special way of receiving the grace of the resurrection, we call her Assumption.
Mary, Mother of Jesus, pray for us that we may lead holy lives and be received into the glory of the resurrection.