Our knowledge of God is incomplete without knowledge of the Son and the Spirit, who are co-equal and consubstantial with the Father. So for us to know God truly and fully we must know the Godhead which makes up the Trinity. We know that if we have seen Jesus we have seen the Father, that to know Jesus is to know the Father; and that the Holy Spirit is at the same time both the Spirit of God and the Spirit of Christ. Knowledge of each has its own special place, function, and application as each member of the Godhead has their own special place, function, and role.
We see their work in salvation (I Peter 1:1-2, Ephesians 1:3-14), creation (Genesis 1:1-2, 26; John 1:1-3), the earthly ministry of Christ (Matthew 3:16-4:1), and Christ's sacrifice (Hebrews 9:14), just to name a few. So understanding the Father, Son, and Holy Spirit within the context of their membership in the Godhead, will give us insight into the profoundness of the person of God.