I'm confused about the whole Cephas thing. Who is he again and what does he relate to?
The Apostle Peter.
Like Buddy said:
John 1:40-42 explains it all ...
40 Andrew, Simon Peter’s brother, was one of the two who heard what John had said and who had followed Jesus. 41 The first thing Andrew did was to find his brother Simon and tell him, “We have found the Messiah” (that is, the Christ). 42 And he brought him to Jesus.
Jesus looked at him and said, “You are Simon son of John. You will be called Cephas” (which, when translated, is Peter).
Cephas (Aramaic) = means "rock" = Petros (Greek) = Peter (English version of 'Petros') = the Apostle Peter
Also the same person from Matthew 16:16-18 ...
13 When Jesus came to the region of Caesarea Philippi, he asked his disciples, “Who do people say the Son of Man is?”
14 They replied, “Some say John the Baptist; others say Elijah; and still others, Jeremiah or one of the prophets.”
15 “But what about you?” he asked. “Who do you say I am?”
16 Simon Peter answered, “You are the Messiah, the Son of the living God.”
17 Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven. 18 And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it. 19 I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.”
Who is the same Peter that the Roman Catholic Church recognizes as the first Pope.