Romeo and friends crash a party at Juliet's house--their families are arch enemies. It's a masquerade ball and everyone is wearing a mask. Romeo and Juliet fall in love at the party. Juliet swears her love on her balcony later that night, and she doesn't know it, but Romeo is in the bushes below listening. They swear their love, and plan to marry. However, Tybalt, Juliet's cousin kills Mercutio, Romeo's friend. Romeo, in a rage, kills Tybalt. Romeo is banished from Verona, but he doesn't leave until he meets Juliet at the Friar's place and marries her. They meet later that night at Juliet's house where they are intimate as man and wife. He then leaves for Mantua. In the meantime, Juliet's father has a plan to marry Juliet to Paris. Juliet worries about this since she is already married. She and the Friar, an expert with plants and herbs, mix a potion to make her seem dead. He will send word to Romeo to come get her so they can live elsewhere. Romeo hears Juliet is dead, but not from the Friar. He buys poison on the way to Juliet's tomb. Romeo wants to grieve alone, but finds Paris there also. Sadly, Paris challenges Romeo--Paris dies. Romeo drinks the poison, kisses Juliet and dies. Juliet awakes, sees Romeo is dead, and kills herself with his dagger. The play ends with the families burying their kids and grieving over their mistakes.
Enotes provides a short summary of Romeo and Juliet- if you follow the first link below, you can read it. There is also a longer summary of each act and scene - follow the second link for those summaries. Basically, it is a story of two feuding families. The son of one family falls in love with the daughter of the other, however, and the rest of the play is about them falling in love and trying to be together even though it is forbidden by their families.
Romeo , who is in love with Rosaline, goes to a party in an effort to forget her or to ease his broken heart. He later finds out that she is a Capulet, the rival family of the Montagues. He decides that he loves her anyway and they confess their love for each other during the very famous "balcony scene" in which they agree to secretly marry the next day. Friar Lawrence agrees to marry them in an effort to end the feuding between the families. Unfortunately, the fighting gets worse and Mercutio , a good friend of Romeo's, ends up in a fight with Tybalt , Juliet's cousin. Tybalt kills Mercutio, which causes Romeo to kill Tybalt in an angry rage. For this, Romeo is banished from Verona.
At the same time, the Capulet's are planning Juliet's marriage to Paris. Juliet does not want to marry this man so she arranges with Friar Lawrence to fake her own death with a sleeping potion that will make everyone think that she is dead. Friar Lawrence promises to send word to Romeo to meet her when the potion wears off and to rescue her to Mantua, where Romeo is currently staying. There they would live happily ever after. Unfortunately, Romeo does not receive this message on time and upon hearing of her "death" goes to Juliet's tomb where he drinks poison and dies. When Juliet's potion wears off, she awaken's to find her lover's corpse. She then proceeds to stab herself with Romeo's dagger. The two families find the bodies and their shared sorrow, finally make peace with each other.