The Gospel of John has a unique literary style which focuses on the signs of Jesus’ identity and mission. Some say this can be divided into two books, the Book of Signs, and the Book of Glory.
There are many similarities and differences in the four Gospels. All four Gospels were written Greek, ranging from Mark’s grammatically poor Greek to Luke’s elegant Greek. The Major opponents in Mark, Matthew and John included the Pharisees while Luke just talks about unjust authorities or rich, corrupt people. Mark wrote mostly to Gentiles being persecuted by their faith, Matthew wrote to educated Jews that were believers but argued over the Laws, Luke wrote to Gentile Christians, and John wrote to Jews, Gentiles, and Samaritans alike.
The Synoptic Problem or Synoptic Gospels; Matthew, Mark, and Luke, are very similar to each other. It appears that they tell the story of Jesus from the same point of view while the Gospel of John is written in a different manor. They Synoptic Gospels often have long stretches of identical text making it difficult to explain away by oral traditions. It is assumed that there is some literary dependence or someone copied someone