What it means

And I heard a loud voice in heaven saying: “Now have come the salvation and the power and the kingdom of our God, and the authority of His Christ. For the accuser of our brothers has been thrown down— he who accuses them day and night before our God. They have conquered him by the blood of the Lamb and by the word of their testimony. And they did not love their lives so as to shy away from death.

From Revelation. Read the verses around it when you can.