God has always existed; before the world was created and long after it will be renewed, God was there. There is only one living God though He exists in three persons: The Father, The Son (Word), and the Holy Ghost. The Father is a Spirit so He can't be seen. Along with the other persons of the Trinity, He is omniscient, omnipotent, omnipresent, immutable, perfect, and sovereign. The Son is God also, He was responsible for creating the world and He is responsible for sustaining the world. Before the foundation of the world, it was decided that the Son would humble Himself and come down to the earth in order to save mankind. He was born of a virgin, lived a sinless life, performed miracles, atoned for the sins of the whole world by His sacrificial death, was buried for three days, rose from death, was seen of +500 men, ascended into heaven and is sitting on the right hand of the Father acting as the Advocate and High Priest of all who are His. The Holy Ghost is the third person in the Trinity. He was responsible for giving us the Bible and is now responsible for "reprov[ing] the world of sin, and of righteousness, and of judgment." Once a person is saved, the Holy Ghost then seals, teaches, brings all things into remembrance, and becomes our help in prayer.