In an orchard at the Capulet place, Juliet waits for the Nurse to come back with a message from Romeo. She worries that they might somehow have missed each other.
When the Nurse comes back, she refuses to tell Juliet anything and complains about her aching back. This is an old game between the Nurse and Juliet: they love teasing each other.
The Nurse keeps refusing to tell Juliet what Romeo said until Juliet can't stand it anymore.
Finally, the Nurse gives in and tells Juliet to run to Friar Laurence's cell (a "cell" is just a room) where Romeo is waiting so they can get hitched.
Before the scene ends, the Nurse says she'll "fetch a ladder" for Romeo to climb up so the lovers can spend their wedding night together. She also manages to turn her description of Romeo "climbing" the ladder into Juliet's "bird's nest" into an image of the kind of sex the couple is going to have later that night.