Juliet is supposed to marry Paris, but she does not want to. She goes to Friar Laurence and he gives her a sleeping potion to drink the night before the wedding, so she will appear dead. She would be put in the Capulet tomb, and the Friar would send Romeo a letter to retrieve her. Juliet is mournful and devastated that her parents are making her marry Paris. The Friar is trying to give her hope, but he himself is a little unsure.
Juliet had gone home, and saw that the wedding preparations had gone underway. She tells her father that she agrees to marry Paris, and the Lord moved the wedding from Wednesday to Thursday. Juliet of course is lying, but she is trying to please her father and mother. This infers that Juliet is sneaky, and is willing to lie to her parents to be with Romeo.
She requests that both the Nurse and Lady Capulet let her spend the night by herself. She is about to take the potion, and is a little worried and sees the ghost of her cousin Tybalt. She made a toast to Romeo and drinks it. Juliet in this scene is very scared, but she is willing to do whatever it takes to be with Romeo.
It's the next morning, and they are preparing the wedding, and the Lord tells the Nurse to wake Juliet up. The Nurse sees Juliet was not getting ready, but the Lord had kept setting up for the wedding. We as the audience already know that these wedding plans are a waste, for Juliet planned to get out of the wedding.
The Nurse realizes that Juliet is dead, and mourns and calls for the Lord and Lady. They now have made the wedding a funeral. They put her in the Capulet tomb covered in her wedding flowers. Both us and the Friar know that Juliet is not really dead, but he has to act mournful still.