There is one true God (YHWH) who always was, who presently is, and who forever will be. He is knowable only because he has revealed himself to mankind in a way that is comprehensible for our limited capacities. Both his written revelation (Holy Scripture) and his general revelation (creation) tell us of his eternal power, invisible attributes, and unfailing love. He is eternal, self-existent, immutable (unchanging), all-powerful, and perfect. He exists in three persons: Father, Son, and Holy Spirit. These three persons are of the same essence. They are in unity with one another in their true essence, and yet they are each distinct in personality and role. They are co-eternal in being and nature, and they are co-equal in power and worth. They exist together in perfect and unbroken fellowship as one essential being.
The following Scripture passages (ESV) offer support, clarity, and distinction regarding the triune nature of God:
Hear, O Israel: The Lord our God, the Lord is one.
It is the Lord your God you shall fear. Him you shall serve and by his name you shall swear.
Then Jesus said to him, “Be gone, Satan! For it is written, “‘You shall worship the Lord your God and him only shall you serve.’”
1 Long ago, at many times and in many ways, God spoke to our fathers by the prophets, 2 but in these last days he has spoken to us by his Son, whom he appointed the heir of all things, through whom also he created the world.
1 In the beginning was the Word, and the Word was with God, and the Word was God. 2 He was in the beginning with God. 3 All things were made through him, and without him was not any thing made that was made. 4 In him was life, and the life was the light of men. 5 The light shines in the darkness, and the darkness has not overcome it.
14 And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth.
2 Corinthians 13:14
The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.
Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.
16 And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; 17 and behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”
16 And I will ask the Father, and he will give you another Helper, to be with you forever, 17 even the Spirit of truth, whom the world cannot receive, because it neither sees him nor knows him. You know him, for he dwells with you and will be in you.
1 Paul, a servant of Christ Jesus, called to be an apostle, set apart for the gospel of God, 2 which he promised beforehand through his prophets in the holy Scriptures, 3 concerning his Son, who was descended from David according to the flesh 4 and was declared to be the Son of God in power according to the Spirit of holiness by his resurrection from the dead, Jesus Christ our Lord, 5 through whom we have received grace and apostleship to bring about the obedience of faith for the sake of his name among all the nations, 6 including you who are called to belong to Jesus Christ.
9 And so, from the day we heard, we have not ceased to pray for you, asking that you may be filled with the knowledge of his will in all spiritual wisdom and understanding, 10 so as to walk in a manner worthy of the Lord, fully pleasing to him: bearing fruit in every good work and increasing in the knowledge of God; 11 being strengthened with all power, according to his glorious might, for all endurance and patience with joy; 12 giving thanks to the Father, who has qualified you to share in the inheritance of the saints in light. 13 He has delivered us from the domain of darkness and transferred us to the kingdom of his beloved Son, 14 in whom we have redemption, the forgiveness of sins. 15 He is the image of the invisible God, the firstborn of all creation. 16 For by him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him. 17 And he is before all things, and in him all things hold together. 18 And he is the head of the body, the church. He is the beginning, the firstborn from the dead, that in everything he might be preeminent. 19 For in him all the fullness of God was pleased to dwell, 20 and through him to reconcile to himself all things, whether on earth or in heaven, making peace by the blood of his cross.