Defining who and what God is difficult because God is by nature completely different from what we are. Therefore, we can only describe Him by analogy and cite His attribute as He has revealed to us as found in the Bible. Nevertheless, the Christian God is the only supreme, infinite, eternally self-aware being, who had no beginning nor will He cease to exist, who is non-contingent, transcendent, immutable, and of whom no greater being exists. His attributes include holiness, omniscience, omnisapience (all wisdom), omnipotence, omnipresence, logic, righteousness, justice, mercy, grace, etc. He is revealed to us in the person of Jesus as is described in the New Testament Scriptures.
The revelation of Christ as a manifestation of God is necessary because God is completely other than what we are. God is so different than us that there is no way for us to know who he is unless he reveals himself. This self-revelation is found in the person of Christ who, according to Scripture, is God in flesh (John 1:1, 14 Colossians 2:9) and is the express image of God (Hebrews 1:3). Therefore, God is a God of miracles, perhaps the greatest being the incarnation. The Bible recounts many miraculous events in both the Old and New Testaments which, ultimately, point to Christ as that final revelation of God (John 5:39).
God possesses communicable and incommunicable attributes. Communicable attributes are those qualities of God that we can experience and understand. For example, God loves, and we can love. God hates, and we can hate. The incommunicable attributes of God are those qualities of his nature that we cannot experience. For example, God knows all things; we do not. God is everywhere; we are not. God is all-powerful, we are not.
God is the creator of all things (Isaiah 44:24). He is the one who brought the universe into existence since it cannot bring itself into existence. He alone is God (Isaiah 45:21, 22, 46:9, 47:8). There have never been any gods before Him nor will there be any after Him (Isaiah 43:10, 44:6, 8). God is God from all eternity (Psalm 90:2). In Exodus 3:14, God revealed His name to His people. The name commonly known in English is Jehovah. This comes from the four Hebrew consonants that spell the name of God. (See Tetragrammaton).
God is a Trinity which is the teaching of three distinct and simultaneous persons in the single being who comprises God. The three persons of the Father, the Son, and the Holy Spirit. The Trinity is an earthly manifestation described in Scripture and represents the true nature of God who knows all things (1 John 3:20), can do all things (Jer. 32:17, 27, except those things against His nature like lie, break His word, cheat, steal, etc.,) and is everywhere all the time (Psalm 119:7-12).