Synoptic Gospels

In the New Testament, the gospels of Matthew, Mark and Luke, are written in a very similar style. They are referred to as the synoptic gospels.The forth of the evangelists, John, also tells similar stories, but his style of writing is different. The synoptic problem is to explain why three of the four evangelists have a very similar structure, and the fourth does not.
The strong parallelism among the three gospels suggests they were written at more or less the same time. Or, Matthew and Luke made use of the gospel of Mark as a source.