The Last Judgment is that time where all humanity comes before God to be judged. Those who pass will be with God in heaven for all eternity, while those who do not will be sent away to Hell. In Christian theology, only a personal knowledge of Jesus as Lord and Savior allows for the individual to pass into God's presence.
According to Premillennialism, there are two judgment days. The timing of the two main judgment days, according to Premillenialist teaching, occur right after the First Resurrection and right before the Millennium, and the other judgment occurs right after the Second Resurrection and after the ending of the Millennium, which happens before the Eternal State. The last judgment is called the Great White Throne Judgment. (See Revelation chp. 20)
Revelation 20:4 says "And I saw thrones, and they sat upon them, and judgment was given unto them" and it speaks of those who "lived and reigned with Christ a thousand years. But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection." It does not say that anyone was judged.
Revelation 20:12b, 13b-15 says "and the dead were judged out of those things which were written in the books, according to their works...and they were judged every man according to their works. And death and hell were cast into the lake of fire. This is the second death. And if whosoever was not found written in the book of life was cast into the lake of fire."
Hebrews 9:27-28 is absolute in its teaching: "And as it is appointed unto men once to die, but after this the judgment, so Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him." It does not say "judgments".
Matthew 25:31-32, 46 says, "When the Son of man shall come in his glory, and all the angels with him, then shall he sit upon the throne of his glory: And before him shall be gathered all nations: and he shall separate them one from another, as a shepherd divideth his sheep from the goats:...And these shall go away into everlasting punishment: but the righteous into life eternal."
Islam also has a form of The Last Judgment.