God, also known as Elohim, Jehovah, Yahweh, Deus or Allah, is the sole deity of the Abrahamic religions, which are Judaism, Christianity and Islam. While the religions have differences of God's true way, they all agree that He alone created everything in existence, and that He communicates his will through humans that are prophets, such as Moses, Muhammad and Jesus Christ, with the latter being an Earthly incarnation of Him in Christian belief.
Christianity notably believes in one Trinitarian God, who Has three aspects. The aspects are The Father, The Son (Jesus Christ) and The Holy Spirit.
While all three Abrahamic religions are monotheistic, both Christianity and Islam envision adversarial beings in the form of Lucifer, Satan or Iblis. These adversaries were once angels (Jinn in Islam), who fell from Heaven after a rebellion against God, and became demonic entities. These demons now try to lead humans and their souls away from God, hoping to damn them in the process. They sometimes called as "the gods of the Earth" in the Bible, being able to perform lesser miracles to impress humans. Eventually God will vanquish them, and they are never considered equal to Him.