Q: Who is God?
A: God is:
1- Creator of the universe
2- Law-giver of the world (Physical laws + Law of Requital)
3- Standard for development of human's self
Q: What is God?
A: Our intellects have the limitation. We cannot know anything about God's nature and essence. We cannot even say anything about the reality of a chair or table (we can only see their signs but those signals which affect our sight or touch cannot in their nature be like unto the signals which the signals awake. So what is a 'chair' or 'table'? Again, our intellect cannot comprehend the reality even through physical knowledge).
We cannot pour a jug of water into a small mug and we cannot grasp indefinite God by our definite mind.
Do we need to know the nature of God? No!
We only need to know the God's attributes and adopt them in our limited capacity. So, God is the perfect Standard for development of man's personality and not a deity that people worship or prostrate for him.
Q: Where can find these attributes?
A: Only in the Book of God, the Quran.