There is only one God (John 17:3). He is all-knowing (1 John 3:20b), all-present (Proverbs 15:3), and all-powerful (Mark 10:27). He created everything that exists (Genesis 1:1). He is eternal (Isaiah 40:28) and holy (Leviticus 11:44), one God, existing in three coequal persons: the Father, the Son, and the Holy Spirit (Matthew 28:19, 1 Peter 1:2). Though three persons, He is one God. This is often called the Trinity or Godhead.
The Father is the ‘focal point,' or ‘head' of the Trinity. It was by His power that all things were made and have their life (Ephesians 2:10, 1 Corinthians 8:6). He will bring the end of the world as we know it and all will be judged (Acts 17:31). The Son (John 5:19, 10:18) and Holy Spirit (John 16:13) submit to the Father though they are coequal with the Father.
The Son came to the earth in the flesh (John 1:14) to live the perfect example for us to follow (John 13:15-17), thereby being the perfection of the Old Covenant (Hebrews 5:9, Matthew 5:17). He died for our sins, because in being perfect he was the only one who could fully pay the price of sin (Hebrews 9:12-14). He was crucified, buried, and raised by the Father on the third day after his death (1 Corinthians 15:3-5). He ascended into Heaven (Acts 1:9) where he sits on the throne at the right hand of the Father (Hebrews 12:2) where he is interceding in prayer for all Christians (Hebrews 7:23-25). He will return to the earth to bring judgment upon it (John 5:27, Matthew 25:31-46).
The Holy Spirit is coequal with the Father and the Son (Matthew 10:20, 2 Corinthians 3:17). Though He worked in the lives of men and women before Christ (Numbers 11:14-17, 24-27), it was after Christ that He was poured out on all men (Acts 2:17, 33). It is through Him that we have intimate contact with the Father (Romans 5:5). He was sent in order to teach truth (John 14:16-17), convict the world of its sin (John 16:8), and teach them to remember Christ (John 14:26). He moves in the lives of everyone, but dwells in the hearts of those who are Christians and gifts them (Acts 2:38, 1 Corinthians 12:7-13, Galatians 4:6) as a guarantee of eternal life (2 Corinthians 1:22). It is by His power that Christians are able to change their ways and renew their minds to think on the things of God and not on things of the world (Titus 3:5-7, Galatians 5:16). He prays for God's people on their behalf when they do not know for what to pray, groaning to God all the inexpressible feelings from their hearts (Romans 8:26).