The gospels according to Mark, Matthew, Luke, and John were compiled in the second half of the 1st cent. CE, and, in accordance with contemporary custom, were intended to be read aloud. They were all written to satisfy needs felt in the growing Church, and whether or not the gospels were compiled for the particular community in which each evangelist resided, or whether they were intended for the wider Church, each gospel shows traces of its surrounding culture, e.g. ethnic, linguistic. At first there was just the oral tradition; Jesus himself did not write a word; but parables spoken by Jesus and many of his conversations were remembered and in the early days of the Church these reminiscences were constantly passed on. The store of traditions was drawn on by Christian evangelists who tried to persuade members of the synagogues, and by controversialists in debates. There were new recruits to the Church who wanted to know how it had come about that a good man (Jesus) had suffered death at the hands of the Romans. Moreover this man was being preached as a Saviour who had been raised from the dead! Not surprisingly, when Mark was persuaded, perhaps in Rome, to put in writing the reminiscences that were held in the Church, his gospel was a detailed account of the trials and execution of Jesus, with an introduction containing excerpts of teaching and examples of about a dozen miracles. It was left to Mark's successors to fill out his narrative not only with extended extracts from Jesus' teaching but also with narratives about his birth. The gospel of Matthew follows Mark's order in the main, but incorporates into it much added material in five great discourses of Jesus, edited by the author of the gospel. He makes improvements to Mark's style by pruning verbosity and clarifies some of the Marcan obscurities. The gospel of Luke also uses Mark but less slavishly. So these first three gospels have much material in common, as is demonstrated by comparing them word for word, paragraph for paragraph, in three parallel columns. For this reason they are known as the ‘synoptic gospels’—i.e. gospels that can be viewed together. The fourth gospel (John) is in another category, was almost certainly written later, and is very different in style, content, and theological emphasis. Much of it spells out what in the synoptics appears in disconnected fragments or veiled allusions.
The four gospels did not represent the end of these literary ventures. They were, however, the works which were in due course pronounced by the Church to be parts of the NT ‘canon’; but Gnostics and others promoted rival versions of the Jesus story, such as the gospel of Thomas (c. 140 CE), which was discovered at Nag Hammadi; it is a collection in Coptic of 114 alleged sayings of Jesus but this ‘apocryphal Gospel’ offers the reward of salvation (immortality) to those who gain the right knowledge.
The gospels are not biographies in the modern sense, and the Form Critics maintained that they were not biographies in any sense. But such a negative view cannot be sustained in view of some similarities to contemporary biographies; yet the gospels are differentiated by their religious message (John 20: 31) and their claim that the promises of the OT are fulfilled in the main subject (Jesus) and in the evangelists' hope to influence their readers' lives.