The bible says in the beginning was the Word, and the Word was with God and the Word WAS God. So, God is the Word. Well you ask, what is the Word? The Word is the bible. So what God did was, He took the Word, which is Himself, and put it in a flesh body, which was (and still is) Jesus. See, God the Father, is a spirit, but Jesus, the Son, was a man. Two separate beings, yet they are one. It may be a little difficult to comprehend, and it is, when you look at it in the natural, but you have to grasp it in the spirit, which expands beyond our natural way of thinking. I'll try to break it down a little bit more for you. Imagine a crumb falling off of a biscuit. The crumb is separate from the biscuit, but yet it came from the biscuit. Two separate beings, yet they are one.
Now I'm going to explain the Holy Spirit as best as I can. The Holy Spirit is the spirit that resides within God the Father, Jesus the Son, and also in born-again Christians here on earth. The Holy Spirit is how we receive His power, its how He lives in us if we're born-again. So, it's His spirit, in us. That is why the bible says, if any man has not the Spirit of Christ (the Holy Spirit), he is none of His. Now when you put God, Jesus, and the Holy Spirit together you get the trinity. Three separate beings, yet they are one.
Now this goes to show how amazing God is, and the glory of His power. He so multifaceted, we can barely wrap our minds around it. It's like trying to comprehend how long eternity is. It's just mind boggling, beyond our imagination. And that's how God is, we can't even begin to grasp His glory.
I hope this helped buddy.