Short answers, pulled from the story.
Septimius Tertullianus was a Roman Christian theologian and writer born in the Roman province of Africa around the year 155. Before writing about the Christian faith, he was a trained lawyer in Carthage who possessed a sharp mind and powerful voice.
Tertullian converted to Christianity around 197 or 198 in a sudden and decisive manner that transformed his personality overnight. He described this event as a violent rupture where he chose to become a soldier of Christ rather than a slow drift into faith.
Tertullian was the first writer in Latin known to use the term trinitas or trinity to describe the relationship between the Father, the Son, and the Holy Spirit. He introduced new concepts such as persons and substance to maintain the distinction of the Son from the Father while arguing they were one in substance.
Tertullian was drawn to the New Prophecy of Montanism around 207 because the movement emphasized strict asceticism and a rigorous moral code. He argued that second marriage was a species of adultery and that sexual relations would disrupt the Christian life, leading him to favor the Montanist sect over the orthodox church.
Tertullian is often called the founder of Western theology and the first Christian author to produce an extensive corpus of Latin Christian literature. His influence on later theologians like Cyprian and Augustine was immense, even though his views on the Trinity and the nature of God were often too radical for the mainstream church to accept.