This is an extension of the other thread "Who is God?"
I ask not who, but what.
Please give a definition of "God".
I am not sure exactly what you want for an explanation of WHAT God is, But let me try, and you can determine how the difference of WHAT and WHO applies.
First God's Personal Name, or Proper Name is JEHOVAH, which means that He causes to become. In the end God causes everything to become exactly as His original purpose stated at Gen 1:26-28.
Jehovah is God's Proper name. In the original writings this name was used over 7,000 times, far more than any other name in the Holy Scriptures. Another way He is described is by the term GOD IS LOVE, 1John 4:8,16. God also has many Proper Adjective names, which are descriptive names, The Almighty, the Creator, Mighty man of War, Sovereign Lord, Jealous God Ex 34:14, a God of vengence, who will repay to everyone according to his works, Rom 2:6,3:5,6, The ROCK, perfect is His activity, Deut 32:4, Father, Matt 7:21-23, 16:17, Savior, and ONLY GOD, Jude 25, John 17:3, 1Cor 8:6, Eph 4:6.
There are other names, but these are enough to explain exactly, both WHO and WHAT God is.