Of the Trinity, the Holy Spirit is the aspect of God I have the most trouble explaining to a non-believer. In my younger days, he was called the Holy Ghost and that caused even more confusion. A Christian is not possessed by a spirit, even a holy one. When we become followers of Christ, God places his Spirit in our heart to guide and empower us if we choose to respond to his promptings. We still have our God given free will. I have learned the hard way when the Holy Spirit prompts me I only have two choices, do it or regret it.
My first experience with the Holy Spirit was as a new Christian at age eleven. Reading the King James Bible (the only translation we had back then) with full understanding. There is no other explanation for that. I soon learned to recognize when God is prompting me to do or say something. It is not a voice or picked up by any of my senses, but it comes straight from my heart to my mind and I know the source.
After all of these years, the Holy Spirit guides my fingers on the keyboard as I write this blog. I know it is his message and not mine because when I read a post from several years ago I think, “Boy, that is good, I wish I had thought of that.”