Most people become perplexed and confused when faced with the biblical concept of the one true God comprising three persons. The reason is that we have finite minds and live in a finite world where everything including our lives has a beginning and an end. We understand only what we experience and know about the natural world around us.
God said, “Let us make man in our image, after our likeness; and let them have dominion over the fish of the sea, and over the birds of the air, and over the cattle, and over all the earth, and over every creeping thing that creeps upon the earth.” So God created man in his own image, in the image of God he created him; male and female he created them. (Genesis 1:26-27)
Consider if you will, for the sake of your own understanding, that the Creator of the universe as we know it, exists in an eternal parallel universe or another dimension outside the constraints of time where there is no yesterday no tomorrow, only an eternal present. We can know from the first chapter in Genesis that the Creator refers to himself as "US" indicating that more than one person is the co-creator of all things. We know that God the father, is the primary person of great magnificence and almighty power that emanates through the will of His Spirit. "God is spirit, and those who worship him must worship in spirit and truth.” (John 4:24)
He is also imbued with another persona, the Son. They have always co-existed in a dimension outside of time in an eternal universe.
The thought that man is created in the image of God may seem overwhelming but it will be helpful in understanding the trinity. It has nothing to do with our appearance being at all anything like God, however it alludes to the fact that we are tripartite beings just as God is. We have a Spirit just as God the Father is Spirit, our spirit comes from God and gives us our innate God consciousness. We have a physical body just as God the son, and we have a soul or ego from which emanates our personality. Three distinct parts in one being that all work together.
God knew beforehand that man would fail Him (sin), He established the penalty of death for mankind's failure. In order for God to rescue His creation by offering Himself to pay the price for all the sins of mankind He would have to leave His eternal place and be born into this dimension governed by time, this is the motive and destiny of His Son, as the sacrifice and payment for the sins of man.
"In many and various ways God spoke of old to our fathers by the prophets; but in these last days he has spoken to us by a Son, whom he appointed the heir of all things, through whom also he created the world. He reflects the glory of God and bears the very stamp of his nature, upholding the universe by his word of power. When he had made purification for sins, he sat down at the right hand of the Majesty on high." (Hebrews 1:1-3)
In human terms it is difficult to contemplate a virgin giving birth, and yet not difficult at all for God who spoke the entire universe and everything in it into existence from nothing willed through His Holy Spirit.
In the sixth month the angel Gabriel was sent from God to a city of Galilee named Nazareth, to a virgin betrothed to a man whose name was Joseph, of the house of David; and the virgin’s name was Mary. And he came to her and said, “Hail, O favored one, the Lord is with you!” But she was greatly troubled at the saying, and considered in her mind what sort of greeting this might be. And the angel said to her, “Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bear a son, and you shall call his name Jesus. He will be great, and will be called the Son of the Most High; and the Lord God will give to him the throne of his father David,and he will reign over the house of Jacob forever; and of his kingdom there will be no end.” And Mary said to the angel, “How shall this be, since I have no husband?” And the angel said to her, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be called holy, the Son of God. (Luke 1:26-35)
Hopefully the foregoing will give us all new insights as we celebrate the birth of Jesus, Christ the Savior who is also known to many Jews as Yeshua the Messiah.