The four Gospels were written at different times and for different reasons, directed to different audiences. By becoming aware of the particular areas of emphasis addressed in each of the Gospels, one may find greater understanding of the messages being taught in the scriptures.
The Gospel according to Mark is the earliest of the four. Mark's Gospel is the shortest of the four, filled with action and activity more than with sermons and lectures by Jesus. Mark's immediate audience may have been Gentile Christians living in or around Rome. Mark takes pains to translate Aramaic words used by Jesus that would be unfamiliar to Gentiles, explains Jewish customs, and seems to emphasize preparation for coming hardships and persecutions. As the Christians of Rome were severely persecuted, they would have found reassurance and strength from reading "whoever wants to save his life will lose it, but whoever loses his life for me and for the gospel will save it." (Mark 8:35)
The other Gospels contain other particular focuses. The Gospel according to Matthew was directed primarily to Jewish readers and uses numerous references from the Old Testament to demonstrate that Jesus was the Messiah expected by the Jews. The Gospel according to Luke was written as "an orderly account for you, most excellent Theophilus" (Luke 1:3). Theophilus was apparently a high Roman official and a believer, as the name "Theophilus" means "one who loves God." Luke wrote his Gospel as a source of information and instruction for Theophilus in particular, but with the intent of clarifying the stories about Jesus and strengthening the faith of all believers.
The Gospel according to John is very different from the other three. John's Gospel focuses on "signs" manifested during Jesus's ministry that prove His fulfillment of prophecy as the Son of God.