Paul (Hebrew name: Saul) was an apostle of Jesus Christ and the author of most of the New Testament.
John was one of the 12 apostles, the author of the fourth gospel, three letters, and the book of Revelation.
Peter (aka Simon Peter, Simon, Cephas) was one of the 12 apostles of Jesus Christ and the author of 2 letter in the New Testament.
Luke was a Gentile physician who accompanied Paul on his travels and wrote the third gospel and Acts.
John Mark was a companion of both Paul and Peter, and a cousin of Barnabas and the author of one of the four gospels.