Why does Juliet have a nurse? What are her duties?

"The nurse pretty much brought Juliet up. Woman of high social stature didn't spend time with their kids. The nurse was originally hired as a "wet nurse" so she could breast feed Juliet. The nurse is Juliet's closest confidant. In times of trouble, Juliet turns to the nurse first. Juliet is distant from her mother. Juliet's mother in fact doesn't really know how to speak of anything of substance with her own daughter. This is why she requests the nurse be present when she informs Juliet of Paris."