* Gang warfare: The Sharks and the Jets are both violent gangs and they are constantly fighting with each other. These fights often result in injuries and even death.
* Love and romance: Tony, a member of the Jets, falls in love with Maria, the sister of Bernardo, the leader of the Sharks. This love is forbidden by both gangs and it leads to even more conflict and violence.
* Poverty and class inequality: The Sharks and the Jets are both poor and working-class people. They feel like they are being left behind by the rest of society and they are frustrated and angry. This frustration and anger often manifests itself in violence.