A gospel is a written account of the career and teachings of Jesus of Nazareth. "Gospel", meaning "good news", as does the Greek εὐαγγέλιον, euangelion., originally meant the Christian message itself, but in the 2nd century it came to be used for the books in which the message was set out. The four gospels of the New Testament — Matthew, Mark, Luke and John — are almost our only source of information on Jesus, and thus occupy a uniquely important place in Christianity. They were all written in the period between c.70 AD and the end of the 1st century, by anonymous authors, and stand at the end of a process of oral and written tradition that began on, or even before, the death of Jesus. For various reasons modern scholars are cautious of relying on them uncritically, nevertheless, they do provide a good idea of the public career of Jesus, and critical study can attempt to distinguish the original ideas of Jesus from those of the later authors.
In the immediate aftermath of Jesus' death his followers expected him to return at any moment, and certainly within their own lifetimes. In consequence there was little motivation to write anything down for future generations, but as eyewitnesses began to die, and as the missionary needs of the church grew, there was an increasing demand and need for written versions of the founder's life and teachings. The stages of this process can be summarised as follows:
Given this history, it is almost certain that none of the four gospels were written by eye-witnesses. Evidence of this can be seen in the conflicts between them: to take a few examples, according to the synoptic gospels, Jesus' mission took one year, was spent primarily in Galilee, and climaxed with a single visit to Jerusalem at which he cleansed the Temple of the money-changers, while in John, Jerusalem was the focus of Jesus' mission, he visited it three times (making his mission last three years rather than one), and the cleansing of the Temple took place at the beginning rather than the end of the ministry.
The first three gospels are called the "synoptics", from a Greek phrase meaning "seen together", because they put the events of Jesus' life in the same order and have many of the same stories and sayings, often in the same or very similar words. The usual way of explaining this similarity is that Mark was written first, and that the authors of Matthew and Luke, acting independently, used Mark plus a collection of sayings called the Q document and additional material unique to each called the M source (Matthew) and the L source (Luke). Mark was probably written c.AD 66–70, during Nero's persecution of the Christians in Rome or the Jewish revolt, and the general consensus on the dates of both Matthew and Luke is around AD 85-90. Early Christian tradition names the author of Mark as John Mark, a companion and interpreter of the apostle Peter, but most modern scholars regard the authorship as unknown. The consensus has equally rejected the idea that Luke was written by a companion of the apostle Paul, or that Matthew was by an apostle (the superscription "according to Matthew" was added some time in the 2nd century).