Pastor walks his children through Westminster Shorter Catechism question 6—especially explaining how we must guard true monotheism, as we think about the God Who has revealed Himself, in Christ, as Triune.
Q6. How many persons are there in the Godhead? 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.