For any book of the Bible, it is important to know its context – who wrote it and when, why it was written and the nature of the original hearers or readers. This is especially important with the Gospels because each writer has his own individual personality that shines through the material along with the themes and emphases that are important to him (or his readers). Each Gospel is written for a reason and each author makes this explicit in one way or another. The books are different in length as well as character and they draw on a different combination of sources, thus each has some individual material whilst sharing much with others. This is particularly the case with the Synoptic Gospels (Matthew, Mark and Luke), but not so much with John who has his own particular style, language, material and purposes.
Introduction to the Gospel of Matthew