Shorter Catechism Q. 6. How many persons are there in the godhead? A. There are three persons in the Godhead; the Father, the Son, and the Holy Ghost; and these three are one God, the same in substance, equal in power and glory.
Commentary: The word “godhead” is an older word that the KJV uses in Acts 17:29. It refers to deity (NRS) or the divine being (ESV) or divine nature (NAU). The Modern English translation of the Shorter Catechism uses the word “God” instead of “godhead.” Since there is only one God and thus only one divine nature/essence/being, this question is asking how many persons there are within the one God. Unitarians say there is only one person. Trinitarians say there are three persons. Christianity is trinitarian. There are three persons in the one God: the Father, the Son, and the Holy Ghost.
The term “Ghost” is another older term that was used by the KJV. The word “ghost” today conjures up images of Caspar the Friendly Ghost or the ghosts from the Harry Potter movies/books who are visible spirits of deceased people that can’t physically interact with the living world. We should not think of the Holy Ghost like that, which is why today we refer to the third person of the Trinity as the Holy Spirit.
The three persons are distinct from one another and relate personally to one another. The Father, for example, loves and talks to the Son and vice versa. The persons are not different modes or ways the one God relates to the world. It is not as if God is one person with three different roles so that he sometimes acts as a Father, and then as a Son, and then as a Spirit. God is not one person. There are three persons in the godhead.
Although the three persons are distinct, they are not three gods. There is one being who is God, and all three divine persons share and exist within that one being. This is not to say that each person is one third of the divine being. Rather, each person is or exhausts the divine being, each person has all the divine attributes, and each person is in the other two. They are the same in substance. Consequently, when you encounter one person, you encounter all three. If you have seen me, Jesus says, you have seen the Father. Furthermore, there is no subordination within the divine being. One person is not less than another person. All three are equally God and therefore they are equal in power and glory.