It is a picture of the way our prayers rise before God and are accepted by Him as something pleasant and sweet. Angels assist in the presentation of our prayers before God. They rise with the Spirit's power, the Son's mediation, and the assistance of the angels in heaven. Verse 3 suggests that the prayers have already been accepted by God. We are not to understand this as suggesting that it is necessary for the angels to mediate the prayers of the saints.
Prayer changes the world.
Prayer reenters history with incalculable effects. Our earth is shaken daily by it. The silence is broken by the noise of trumpets. The nature of the Day of Judgment is vengeance, the vengeance of God. It is the Day when God vindicates His justice.