Biblically speaking, Christ has told us: "God is a Spirit: and they that worship him must worship Iin spirit and in truth." (John 4:24). We are also told in 1 John 4:8: "He who does not love does not know God, for God is love."
But the question here is not asking you to regurgitate the Bible. It's asking you to internalize what you are told from the Bible, from your own experiences with God, and express your own understanding of who God is. This is a question we could probably ask 100 Christians, and get 100 different answers to, and they'd all be correct - as this is a pretty personal question.
Then again, looking at the much bigger picture, we also know, "For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life." (John 3:16) This isn't just an individual God, but God for the whole world.
Does that change your understanding about who God is?