The Theotokos falls asleep, and the Apostles are gathered to her bedside from the ends of the earth. The Lord Himself receives her soul.
Notice what this feast teaches us. The Christian death is not extinguishment. It is a falling asleep, watched over by the Lord. The Theotokos is the first to be assumed — and she is the icon of what awaits every soul that has loved her Son.
We pray her prayers because she stands closer to His ear than any of us. And we pray that, like her, our own falling asleep will be in the hand of God.