My personal understanding of how God is one and also triune. God is one in the idea that compared to other gods, God is singular. God is triune in the idea that God works in specific ways and those are operated by the Father, the Son, and the Holy Spirit. But the Father, the Son, and the Holy Spirit are God in unity and individually. In a better picture I could paint, the Father is the Voice, the Son is the Doer, and the Spirit connects us directly to God plus fulfills a similar role as the Son. The difference being one was in the flesh and the other is in the Spirit. Both are Comforters to us.