This is a reference to the characters in Romeo + Juliet. In it gives the characters, where they stand in the feud and their characteristics. Very useful for characters revision after doing R+J a while back.
We tend to think of Shakespeare as the timeless author who did nothing but craft beautiful, hilarious plays for our enjoyment. However, the fact is that he was a human being affected by the attitudes and beliefs of his time, just like the rest of us. Sorry to burst your Shakespearean bubble of bliss!