Okay, first of all this is a religious question. But I'm a Muslim and u have a question about Christianity, so I can't ask this in a Muslim forum.

So, I was a Christian before, I went to church and everything but I never knew the whole thing about Christianity only enough to disagree. I did read the Bible due to Bible study but somehow I just missed some part.

So my question is: what role does the Holy Ghost play in Christianity? Who exactly is he? And what is written in the Bible about him?

I don't agree in the holy trinity but I'm just curious to know. I feel like as a former Christian I should know.

Please no rude comments, I really just want to educate myself