Introduction to the Gospels (Matthew-John)
The Gospels have a genre parallel in the ancient world that was called the bios. This was ancient biography. Rather than focusing on physical description and tracing psychological thinking and personal development like modern biographies, a bios highlighted the key events that surrounded a person and his teaching. That is very much what the Gospels do. The key characters are Jesus and God, as Jesus carries out the plan of the Father.
Even though the Gospels each offer varying accounts they all share the view that Jesus is the promised Messiah uniquely related to God to bring His promise and salvation. Three of the Gospels (called Synoptics because they overlap at many places) tell the story of Jesus “from the earth up”, gradually depicting how one can see His unique relationship to the Father. Mark starts with John the Baptist, while Matthew and Luke start with Jesus’ unique birth. John, however, tells the story very much “from heaven down.” He starts with the preincarnate Word becoming flesh. His presentation of Jesus as the Son of God is more direct and explicit. The Synoptics allow the reader to gradually see this idea, much in the manner people come to realize gradually who Jesus is. This difference in how the story unfolds does not represent a conflicting account of Jesus, but simply a distinct perspective on how to highlight who He is and what He has done.
(The above excerpt is from the ESV Study Bible, page 1811, pp.2 & 5)