It is one God one power. Although it is not a perfect example it is like a light. The source of the light is the Father. It's radiation, the rays are Jesus Christ. The light which disperses everywhere is the Holy Spirit. One God three persons. God appeared to Abraham as three angels. Jesus said to his disciples: (Matthew 28:19): "Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit." It is one light one God, three expressions three persons. (1 John 5:7 (NKJV)): "For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one." The three persons of the Holy Trinity are different.
The Father is Almighty, Maker of heaven and earth of all things visible and invisible. He is unbegotten(unborned). He is a spirit, true light. He is invisible, unperceived, immaterial, indifferent, incomprehensible. God the Father created us to glorify Him to sing hymns to Him to pray and praise Him. Also He wants us to love Him with all our hearts, mind, body and soul and love other people as we love ourselves. He hates those who hate He loves those who love. He loves us so much that He sent His only begotten Son to be punished by crucifixion. He resurrected His Son and seated Him on a throne at His right hand side.
Jesus Christ is the Son of God the only begotten begotten of the Father before all worlds and time. That is Jesus, as God, has one parent: the Father. Christ is of one essence with the Father same substance with the Father. Saint Paul describes Christ as the brightness of the glory of the Father. Virgin Mary conceived of the Holy Spirit and became pregnant of Christ. She did not conceive of Christ but of the Holy Spirit according to the scriptures (Matthew 1:18). This means that the Holy Spirit is the activity of God.
The Holy Spirit proceeds from the Father (John 15:26) it's source is the Father and is in all places and fill all things. In the Nicene Creed it is mentioned that the Holy Spirit "spoke by the prophets". It is the activity of God. Also the Holy Spirit is our comforter, helper, advocate, supporter, guardian, sympathizer, reliever. The experience you feel from God is the Holy Spirit, only the Holy Spirit. What you sense, feel. What is resulting from God on you is the Holy Spirit. You look at the sun the sun is far away what falls on the retina of your eye, the picture which is formed, the light (Holy Spirit). The manifestation (show) of God to man is the Holy Spirit. The mother of God was found to be pregnant through the Holy Spirit and gave birth to Jesus (Matthew 1:18). She was not found pregnant through Jesus Christ who always existed, Jesus existed before time. This shows that the Holy Trinity is one God. Perhaps the sun is not the perfect example. The Holy Trinity consists of 3 different persons. This was revealed in the baptism of Jesus when the voice of the Father was heard. Jesus was there and the Holy Spirit appeared as a dove (Mark 1:9-11). When we pray and we are in repentance it is the Holy Spirit we feel. What do we feel? We feel love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control (Galatians 5:22-23). The Holy Spirit is mentioned in the Old Testament some of the cases are: (Psalm 51:11): "Do not cast me from your presence or take your Holy Spirit from me." (Isaiah 63:10-11): "Yet they rebelled and grieved his Holy Spirit. So he turned and became their enemy and he himself fought against them. Then his people recalled the days of old, the days of Moses and his people— where is he who brought them through the sea, with the shepherd of his flock? Where is he who set his Holy Spirit among them," (Isaiah 42:1): "Here is my servant, whom I uphold, my chosen one in whom I delight; I will put my Spirit on him, and he will bring justice to the nations." (Joel 2:28): "And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions." (1 Samuel 10:10): "When he and his servant arrived at Gibeah, a procession of prophets met him; the Spirit of God came powerfully upon him, and he joined in their prophesying." (Numbers 27:18): "So the Lord said to Moses, “Take Joshua son of Nun, a man in whom is the spirit of leadership, and lay your hand on him." (Isaiah 11:1-3): "A shoot will come up from the stump of Jesse; from his roots a Branch will bear fruit. The Spirit of the Lord will rest on him— the Spirit of wisdom and of understanding, the Spirit of counsel and of might, the Spirit of the knowledge and fear of the Lord— and he will delight in the fear of the Lord. He will not judge by what he sees with his eyes, or decide by what he hears with his ears;"
I wrote the above with fear because the heresies started from the interpretation of the Holy Trinity.
Prayer to the Father:
Our Father, who are in heaven, hallowed be Your Name. Your Kingdom come. Your will be done, on earth as it is in heaven. Give us this day our daily bread; and forgive us our trespasses, as we forgive those who trespass against us; and lead us not into temptation, but deliver us from evil.
Prayer to Jesus Christ:
Christ, the true light, who enlighten and sanctify every person who comes into this world. Abide in us the light of your face so as to see in it the inaccessible light, and direct our steps to keep your commandments.
Prayer to the Holy Spirit:
O Heavenly King, O Comforter, the Spirit of Truth, who are in all places and fill all things, the treasury of good things and the giver of life: Come and abide in us, cleanse us from every stain, and save our souls, O Good One.
The Creed of Saint Athanasius:
Whosoever will be saved, before all things it is necessary, that he hold the Catholic (Catholic: open to everybody, universal, it does not mean Roman Catholic) Faith. Which faith, except everyone do keep entire and inviolate, without doubt he will perish everlastingly. Now the Catholic Faith is this; that we worship One God in Trinity, and Trinity in Unity. Neither confounding the Persons, nor dividing the substance. For there is one Person of the Father, another of the Son, another of the Holy Spirit. But the Godhead of the Father, and of the Son, and of the Holy Spirit, is all One; the Glory equal, the Majesty co-eternal. Such as the Father is, such is the Son, and such is the Holy Spirit. The Father uncreate, the Son uncreate, the Holy Spirit uncreate. The Father incomprehensible, the Son incomprehensible, and the Holy Spirit incomprehensible. The Father eternal, the Son eternal, and the Holy Spirit eternal. And yet they are not three eternals, but one eternal. As also they are not three uncreates, nor three incomprehensibles; but one uncreate, and one incomprehensible. In like manner the Father is almighty, the Son almighty, and the Holy Spirit almighty. And yet not three almighties, but one almighty. So the Father is God, the Son is God, and the Holy Spirit is God. And yet they are not three Gods, but one God. So likewise the Father is Lord, the Son is Lord, and the Holy Spirit is Lord. And yet they are not three Lords, but one Lord. For like as we are compelled by the Christian verity to acknowledge every Person by Himself to be God and Lord; so we are forbidden by the Catholic religion, to say there are three Gods, or three Lords. The Father is made of none, neither created, nor begotten. The Son is from the Father alone, not made, nor created, but begotten. The Holy Spirit is from the Father, not made, nor created, nor begotten, but proceeding. So there is one Father, not three Fathers; one Son, not three Sons; one Holy Spirit, not three Holy Spirits. And in this Trinity, there is nothing before or after, nothing greater or less; but the whole three Persons are co-eternal together and co-equal. So that in all things, as is aforesaid, the Unity is to be worshipped in Trinity and the Trinity in Unity. He, therefore, that will be saved, must thus think of the Trinity. Furthermore, it is necessary to everlasting salvation, that he also believe rightly the incarnation of our Lord Jesus Christ. Now the right faith is, that we believe and confess that our Lord Jesus Christ, the Son of God, is both God and Man. He is God of the substance of the Father, begotten before the world; and He is man of the substance of His mother, born in the world; Perfect God and perfect man; of reasonable soul and human flesh subsisting. Equal to the Father according to His Godhead; and less than the Father according to His Manhood. Who, although He be both God and Man, yet He is not two, but one Christ; One, not by the conversion of the Godhead into flesh, but by the taking of the Manhood unto God; One altogether, not by confusion of substance, but by unity of Person. For as the reasonable soul and the flesh is one man, so God and Man is one Christ. Who suffered for our salvation, descended into hell, rose again the third day from the dead. He ascended into heaven; He sitteth at the right hand of God the Father Almighty; from whence He shall come to judge the living and the dead. At whose coming all men shall rise again with their bodies, and shall give an account of their own works. And they that have done good shall go into life everlasting; and they that have done evil, into everlasting fire. This is the Catholic faith, which except a man believe faithfully and steadfastly, he cannot be saved. Glory be to the Father, and to the Son, and to the Holy Spirit. Amen.
The Nicene Creed, the symbol of faith:
I believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible; and in one Lord Jesus Christ, the Son of God, the Only-Begotten, begotten of the Father before all worlds, Light of Light, Very God of Very God, begotten, not made; of one essence with the Father; by whom all things were made: who for us men and for our salvation came down from heaven and was incarnate of the Holy Spirit and the Virgin Mary, and was made man; and was crucified also for us under Pontius Pilate, and suffered and was buried. The third day He rose again, according to the Scriptures; and ascended into heaven, and sits at the right hand of the Father; and He shall come again with glory to judge the living and the dead; whose Kingdom shall have no end. And I believe in the Holy Spirit, the Lord and giver of life, who proceeds from the Father, who with the Father and the Son together is worshiped and glorified, who spoke by the prophets. And I believe in One Holy Catholic and Apostolic Church. I acknowledge one baptism for the remission of sins. I look for the resurrection of the dead and the life of the world to come. Amen.