Straight Edge
Straight Edge is a philosophy in which participants abstain from the vices of the modern world. What these actual vices are is subjective, but most commonly, followers will keep well away from alcohol, nicotine, other drugs, and sometimes premarital or promiscuous sex. Thought to have stemmed from the beliefs of Minor Threat front man Ian Mackaye, nowadays Straight Edge is held all over the world throughout numerous different subcultures. It's also believed that The Modern Lovers helped plant the seeds of Straight Edge with their song "I'm Straight".
It has at times been accused of initiating violence, particularly in the Hardcore Punk scene, sometimes causing it to be labeled a gang. Nowadays, however, Straight Edge is largely peaceful, if occasionally Holier Than Thou.
It is notable that MacKaye himself has claimed many times to have never intended to start "Straight Edge" as a social movement and, despite continuing to live a clean lifestyle to this day, he does not consider himself a part of it.
Compare Smug Straight Edge and Straight Edge Evil. See also The Teetotaler.