God is one. He is uniquely one, for He is three Persons in one God. God is Trinity. He is Family and Community.
God is a community of eternal begetting and "begottenness." The Father has been begetting and is always begetting the Son (Jn 3:16, RSV). Therefore, the Son is uniquely begotten, and the Holy Spirit is the eternal Fruit of this love of the Father and the Son.
God is a community of eternal sending. The Father has been sending and is always sending Jesus and the Holy Spirit; Jesus also is always sending the Holy Spirit (see Jn 20:21; 14:26; 16:7).
God is a community of eternal witnessing. The Spirit witnesses to the Son (Jn 15:26), Who is the faithful and true Witness (Rv 1:5) of the Father, Who also witnesses for Jesus (Jn 5:37; 8:18).
God is Triune Community, and the relationships in this Community are unique. We can understand them enough to know that we can never understand them very well. God is transcendent. His triune life is the mystery of mysteries. Yet He has chosen us to live in Him and in Trinitarian love. Praise the Holy Trinity!