1) The psalm celebrates God giving the king victory in battle and granting his desires. The king rejoices in God's strength and salvation.
2) Commentators discuss how the victory is attributed solely to God's power, not human strength. God's answer to the king's prayers in the previous psalm brought him great joy.
3) The psalm is applied both to David's victories and looking forward to the ultimate victory and salvation brought by the Messiah, Jesus Christ.