Since Juliet couldn´t marry Paris, a plan was made. This was for Juliet to take a potion that made her appear dead. Then, when her body was taken away in a casket, Romeo was supposed to be there to open it when the pill wore off, so they can be together.
However, Romeo didn´t know that Juliet wasn´t actually dead, so he killed himself by drinking poison.
Then, when Juliet woke up she saw that Romeo had killed himself. So, she took a dagger and stabbed herself.
After everything that happened, it brought the Capulets and Montagues together. The Capulets put up a statue of Romeo and the Montagues put up a statue of Juliet.