Gog and Magog: The Ya'juj and Ma'juj in Arabic.
Gog and Magog are descendants of Adam who will appear before the end of the world.
"Ya'juj and Ma'juj or Gog and Magog are mentioned in the Qur'an in two places in surat al-Kahf 18:94 and in surat al-Anbiya' 21:96. There are several ahadith of the Prophet (peace and blessings be upon him) about them. Gog and Magog are also mentioned in the Bible in the book of Ezekiel chapters 38-39. Some commentators of the Qur'an under the influence of the Bible tried to identify them with the people of Russia and Caucasia, but there is no basis for this neither in the Qur'an nor in the Hadith. We do not need to identify Gog and Magog with any nation or race. It seems that it is a generic name for some wild, unruly, barbaric, uncivilized and un-religious people. They were causing trouble in the past and then again they or some people like them will cause some mischief before the end of the world. It is reported in the ahadith that Imam Mahdi and Jesus (may Allah be pleased with both of them) will destroy them and then peace will prevail on this earth. May Allah protect us from their trials, Ameen."
Elaborating on this, we’d like to cite for you the following:
“Gog and Magog (two tribes or two peoples) will appear at the time of the second coming of Jesus son of Mary (peace be upon him) before the end of the world, soon after the Dajjal (anti-Christ). Almighty Allah will destroy them all in one night, in response to the supplication of Jesus.
Abu Hurayrah (may Allah be pleased with him) reports that the Prophet (peace and blessings be upon him) said: “Every day, Gog and Magog try to dig a way out through the barrier. When they begin to see sunlight through it, the one who is in charge of them says, ‘Go back; you can carry on digging tomorrow,’ and when they come back, the barrier becomes stronger than it was before. This will continue until their time comes and Allah wishes to send them forth. They will dig until they begin to see sunlight, then the one who is in charge of them will say, ‘Go back; you can carry on digging tomorrow, Insha’Allah.’ In this case, he will make an exception by saying Insha’Allah, thus relating the matter to the Will of Allah. They will return on the following day, and find the hole exactly as they left it. They will carry on digging and come out against the people. They will drink all the water, and find the hole exactly as they left it, and the people will entrench themselves in their fortresses. Gog and Magog will fire their arrows into the sky, and they will fall back to earth with something like blood on them. Gog and Magog will say, ‘We have defeated the people of earth, and overcome the people of Heaven.’ Then Allah will send a kind of worm in the napes of their necks, and they will be killed by it... ‘By Him in Whose Hand the soul of Muhammad is, the beasts of the earth will become fat.’” (Reported by At-Tirmidhi, Ibn Majah, and Ahmad)