The question really is, "Who, is the Holy Spirit?" One key belief to identify "true" Christianity or Christ Followers, would be the belief in something you may have heard before, called the Trinity or a Triune God or how about this, One God Who has three distinct persons.
1. God the Father
2. Jesus Christ (God the Father coming to earth in Human form - born of a virgin, fully man and fully God)
3. The Holy Spirit (God working in those Who believe in Christ - God invisible)
I have heard this analogy to describe what the Triune Oneness of God means and it helped me.
One Egg is one egg, but it has three distinct parts:
1. the shell
2. the white
3. the yolk
More detailed information about the Holy Spirit, can be found here at the bottom of the page: The Trinity