In Christianity, the Holy Trinity includes the Father, the Son, and the Holy Spirit, or -- synonymously -- God our Lord, Jesus Christ our Lord and Savior, and the Holy Spirit. Though Christianity and the Bible teach that each member of the Holy Trinity perform separate functions, they both also teach us that they are one body in Heaven. Each is eternal, everywhere, all powerful, infinitely wise, infinitely holy, infinitely loving, and all knowing; and, the etymology is that The Father is God; Jesus Christ is God; and the Holy Spirit is God. The Father, however, is not Jesus Christ or the Holy Spirit. Jesus Christ is not the Father or the Holy Spirit, and the Holy Spirit is not The Father or Jesus Christ.
Individually, God is the the Heavenly Father to Jesus Christ and mankind. He is love greater than all Earthly loves, and His Earthly children are born good and equal in His Name, though we all have the potential to sin. Jesus Christ, individually, was born as an Earthly being or child to the Virgin Mary to be a disciple to his Heavenly Father, or to spread His good word. The word, quite simply, was and is love. God spoke to Mary, telling her that she would be the Virgin Mother to the "King." Joseph, Mary's husband, was the foster father to Jesus.
Jesus ultimately died young at the hands of power-seeking disbelievers with a crown of thorns and his hands nailed to a cross. The Bible says that his sacrifice, which was to preach God's word and to love all including sinners despite opposition, gave mankind the gift of eternal life. When he died, he ascended into Heaven to dwell at his Father's side.
Individually, the Holy Spirit serves to guide and protect. When we are faced with difficult dilemmas, Christianity and the Bible urge us to pray to the Holy Spirit that it might guide us in the Godly direction, or the direction that God would choose for us. When one refers to Divine Intervention, the Bible says it is the gift of the Holy Spirit. The Holy Spirit also dwells within mankind, giving us the ability to emote, whether through sadness or joy. When we laugh though we are in crisis, the Bible calls our laughter the work of the Holy Spirit.
Yet, the Holy Trinity is considered to be one embodiment in Heaven. This idea speaks to the mystery that asks us to have faith enough to believe what we cannot thoughtfully or physically conceive. The Bible, though referring to each member of the Holy Trinity individually and, again, with different functions, implores that we have faith that they comprise one being in Heaven.
Often, people mistake the Virgin Mary, or the Blessed Mother, as a third of the Holy Trinity. Though she is not, she is a significant figure in Christianity. People often pray to her for her blessing as Christianity considers all of mankind to be her children as well.