Interpretation: Juliet is distraught because Romeo is a Montague--her family's enemy. Her love for Romeo is so strong, but their love is forbidden--only because of their names. Juliet asks "What's in a name" because essentially a name means nothing, especially when it involves love. If a rose was actually named something different, it would still smell the same.
Literary Devices: Juliet's speech is written in Blank Verse. It could be said that this particular quote is an example of a hyperbole, as she is in quite an exaggerated state when she is speaking to Romeo.