Bible Notes Online - Revelation 20 - ESV
Commentary

v1-3: Following the defeat of the beast and his army (19.17-21), Satan is bound for 1000 years. Satan's main purpose has been to deceive the nations; and we have to say that he has been successful. His power included the ability to perform false miracles, 13.13; 19.20.

Notice that John uses four titles for Satan, pulling together the previously mentioned incidents, and showing a single evil power behind them.

v4-6: For that same 1000 years (v4 NIV margin), Christ rules on the earth with His servants; those who were faithful and those who were martyred, 6.10; 7.13-14; 14.4; 19.8. These have a part in the first resurrection, and are promised life; they have the privilege of reigning with Christ.

v7-8: After the 1000 years, Satan is released for a short time, see v3. He begins his final rebellion, by deceiving the nations, and gathering them to attack the Lord, His people, and His city.

v9: Victory is by the power of the Lord, as in 19.21. Fire comes down to destroy the army, Zech 14.12-15.

v10: The devil, Satan, is cast into the lake of fire (or burning sulphur). The beast and the false prophet are not annihilated, but suffer everlasting torment.

v11-13: All judgment is granted to Jesus Christ, the one who sits on the great white throne. The dead, i.e: those who do not believe, are judged according to their works. This is fair and just, Matt 11.22,24.

v14-15: All are cast into the lake of fire, a place of everlasting torment; their names were not written in the Lamb's book of life.