The Exam expects you to be familiar with the so-called Fourth Gospel (John's Gospel) and the different theories about why it was written and its intended audience.
This is a hymn worshiping the Logos that establishes Christ's pre-existence (he existed before the human life of Jesus); it is interspersed with passages where John the Baptist comments on Jesus being the Word of God.
The Book of Signs (John 1: 19 - John 12: 50)
A series of Signs, Discourses and encounters where the Word of God reveals himself to the world but his own people will not accept him. There are 7 Signs and 7 "I Am" statements that explore their meaning. In addition, there is the important meeting between Jesus and Nicodemus where being 'Born Again' is discussed. This section concludes with the final Sign which is the raising of Lazarus from the dead and the decision of the Jewish High Priest to execute Jesus.
The Book of Glory (John 13:1 - John 20: 31)
The Word of God reveals his Glory by dying on the Cross and returning to God, the Resurrection and his Ascension to a fully glorified Eternal Life that he shares with believers. This is the section where the Beloved Disciple appears. If the sections of the Gospel were originally distinct sources, then this might be the source that comes from the Beloved Disciple's eyewitness testimony.
Epilogue (John 21: 1-25)
A series of Resurrection appearances in Galilee and the concluding testimony of the Beloved Disciple. Since the Book of Glory has already come to a very final conclusion, scholars suggest this section was added later (probably after the Beloved Disciple's death).
Brown believes that these sections may have begun as separate sources but that the final author of the Gospel redacted them together to form a single book.
This is a good example of the way Source Criticism identifies different sources within a text and Redaction Criticism explores how they have been put together by the redactor (editor). The identification of the opening Prologue as a 'hymn' is an example of Form Criticism. Brown is a Catholic priest, but some Christians would object to breaking the Gospel up like this and insist it should be read as a consistent unity.