the characters are not given this information. The audience then sees the action unfolding, aware of the mistakes the characters are making. The audience may feel like they want to yell out, "No! Don't do that!" This tension is what makesRomeo and Juliet so exciting.  

Romeo and Juliet may seem to lack the complexity often associated with Shakespeare's other plays because of its apparent simplistic themes and flow and the foregone conclusion, as indicated in The Prologue to the first act. However, The Prologue ensures that the audience is not fooled by circumstances or appearances, immediately setting out that the lovers will "take their life" (6). The audience is then under no illusion as to the extent of the damage that an "ancient grudge" (3) can do and The Prologue also quickens the pace, revealing how fast matters can spiral out of control, almost unnoticed, until it is too late. It also reveals that Romeo and Juliet become the sacrifice, as if some greater good can be achieved by ending "their parents' strife" (8). The Prologue is also intended to point out that anything that is not clear from the Prologue will become increasingly clear as the play unfolds, which is what Shakespeare means when he says, "our toil shall strive to mend," (14).  

Staging a play with a predictable ending requires action and passion from beginning to end. The Prologue to the second act is the only real interruption to that flow. It gives the audience a chance to prepare itself for the foregone conclusion. However, this prologue also serves to build suspense and reveals how the clash between the "extremities" (Prologue.II.14), being the two warring families, actually fuels Romeo and Juliet's love and strengthens it so that "passion lends them power" (13). This adds irony reiterating and confirming that the "grudge" is responsible for the tragic end. 

Interestingly, there are no further prologues to the subsequent acts as the play requires no further explanation and the series of events completes the cycle. If any member of the audience has any doubts, he or she need only consider the Prologue to Act I and the confirmation of events in the Prologue to Act II to remove confusion. The audience could even get so involved in the events as to wish to shout out to Romeo at the end in order to save him from his fate. The audience is completely absorbed and their own powerlessness makes it even more dramatic.

In the prologue is when we are introduced to the problem of the story, the setting, the characters, and even the ending: The lovers whose houses are divided and in quarrel.

The prologue tells the entire story, so that the audience can in a way expect the tragic ending. However, the setup is also for the purpose of tuning into the story, and feeling the circumstances throughout the play that prevent the ending from being any different.

The prologue in Romeo and Juliet provides important exposition for the audience or reader. Because the play begins in media res—or, "in the middle of things"—it is necessary to provide some background information to make sense of what follows. From the prologue we learn that the Montagues and Capulets are two families of similar socioeconomic backgrounds and reputations ("Two households, both alike in dignity...") who are engaged in a very old feud that continues to wreak havoc across Verona ("From ancient grudge break to new mutiny, / Where civil blood makes civil hands unclean."). We are introduced to the protagonists of the play: the "star-cross'd lovers" who are members of these rivaling factions. We also learn prematurely of their deaths. This is all critical information since the very next scene is, in fact, a brawl between the Montagues and Capulets—one that might seem a bit random or antagonistic without context.

You might wonder why Shakespeare would choose to give away all this information (particularly the end of the play itself!) before the action has even started, and in this case it's significant to remember that this material was meant to be seen on stage and not read. The prologue, which states that there will be "two hours' traffic of our stage," lets a Shakespearean audience (which largely consisted of people packed together in the cheap standing section) how long the play will last—and how long they'll have to hold off from fidgeting!

It is ultimately a testament to the staggering emotional gravity of this work that audience members who already know how the story resolves were (and still are!) happy to sit through the whole performance anyway. In our modern age of "spoiler alerts," it is also fascinating that contemporary audiences who are so overly-familiar with the basic plot of this story and who have seen it re-made and adapted a thousand times over still flock to the original text. Romeo and Juliet is indeed a classic.

As for Benvolio's remark about arriving at the Capulet ball "without-book prologue": Benvolio is simply answering Romeo's question here ("What, shall this speech be spoke for our excuse? / Or shall we on without an apology?") and weighing in on the use of having one's entrance announced. Romeo and his crew will sneak into the ball without pomp and circumstance, and they will allow the other partygoers to size them up "by what they will." This is also a sly reference to the play's prologue. Whereas we begin the play knowing exactly what will be set forth, we enter this scene without this same knowledge. This is a subtle way of suggesting that the tides are about to shift for Romeo and that the events to follow will be a turning point.

In the play Romeo and Juliet, the audience knows the outcome of the play even before we meet the main characters.  The chorus begins the play by presenting the Prologue.  This introduction to the play sets up the story by explaining the plot that is about to take place.  The chorus explains the centuries long feud that exists between the Montagues and the Capulets that will end after a child from each of the warring families falls in love with one another.  However, this will not be our typical happily ever after love story as the two families will only have peace and come together after the deaths of the innocent children.

From forth the fatal loins of these two foes(5)
A pair of star-cross'd lovers take their life;
Whose misadventur'd piteous overthrows
Doth, with their death, bury their parents’ strife.

The chorus speaks the prologue in Romeo and Juliet. The purpose of this prologue is to summarize what will happen in the play. Since the play has many comic moments and is a love story, an audience might be inclined to understand it as a romance, which would imply a happy ending. Shakespeare wants to be very clear from the start that although the play might seem to adhere to the romance genre with the lovers united in harmony at the end, this is not how the plot will unfold. Shakespeare obviously knows that audiences whose expectations are thwarted tend to be unhappy—and possibly overly rowdy in expressing their discontent. He therefore carefully avoids misleading people about the tragic subject of this play. We may read these plays as high art, but Shakespeare needed to make a living, and that meant pleasing his audience.

Shakespeare uses rhyme and alliteration to summarize the play in the prologue. For example, he writes:

From forth the fatal loins of these two foes
A pair of star-crossed lovers take their life,
Whose misadventured piteous overthrows
Doth with their death bury their parents' strife.

The purpose of a prologue is to set the scene.  Unlike prose, which has more freedom to develop the background as the story progresses and move forwards and backwards in time, a play is constrained to scenes in real time.  Therefore, the prologue of a play is meant to give the audience an idea of what the story will be all about.  It can provide background information that cannot be acted out in real-time or would distract from the flow of the play if it were.  It also allows the author of the play the ability to speak directly to the audience rather than having to speak in first person through his/her characters.  In the case of Romeo and Juliet, the prologue not only provides the audience with the background story, but it foreshadows the fate of Romeo and Juliet.  The Chorus, who is not an actual character in the play, speaks the prologue.