In Romeo and Juliet, what is the purpose of the Chorus?

As was the case in ancient Greek theater, the Chorus provides commentary on the play, and its purpose in the Prologue seems to be to tell the audience exactly what is going on and will happen in the play. The Prologue is essentially a plot summary, and what it gives away in suspense by giving away the ending, it makes up for by creating dramatic irony that can be heartbreaking. We know throughout the play that Romeo and Juliet are "star-cross'd," doomed to take their own lives. This makes their tender expressions of love for one another all the more poignant, and their attempts to overcome fate all the more tragic. The second appearance of the Chorus, in Act II, is less clear. It reinforces the idea that the two lovers are struggling against the forces of fate and their family ties. It also emphasizes the power of love to "meet tempering extremities with extreme sweet." In many ways, the Chorus, along with simply relating the key plot elements, reinforces some of the key themes in the play.