And many other signs truly did Jesus in the presence of his disciples, which are not written in this book: But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.– John 20:30-31
John is the “unidentified” disciple whom Jesus loved (John 13:23). He wrote the gospel as well as the three small letters bearing his name, and the Book of Revelation. He was one of the original twelve disciples and the only one to live to an old age. He and his older brother were sons of a man named Zebedee. In Matthew chapter 4, they are with their father in a ship in the sea of Galilee. They are mending their nets when Jesus calls them. They drop their work and follow immediately. He, along with Peter and James, were the only witnesses to the raising of Jarius’ daughter from the dead, the transfiguration, and the agony in Gethsemane. After the persecution in Jerusalem, John is probably centered out of Ephesus.
John’s gospel account is very different than the other three “synoptic” gospels that give a synopsis of the life of Christ. John does not include as many historical details but rather focuses on many important doctrinal and theological points. John’s emphasis is on the fact that Jesus is God. He begins before the incarnation showing that Jesus has always been God the Word. John also shows the dual nature of Jesus, being God and man at the same time, refuting the Gnostic claims just like Luke did.
John records his purpose for writing his gospel account in John 20:31. He desires that his readers have a full understanding of the deity of Christ so that they may live a life of liberty in Jesus. It can therefore be concluded that John was writing to believers who wanted to understand even more deeply Who their Savior was.