"Hardcore kids" are the douch baggiest, faggiest, biggest fake-tough guy assholes you will ever see. They were girls jeans, slip on shoes, studded belts, kiddy-sized t-shirts, and shaggy hair in their faces, with gigantic space making earings, and when they are being "hardcore" they go mosh with other losers in a circle pit wearing bandanas over their faces like they're about to rob a stage coach.
Never try to talk to them about music, because if they don't listen to it, it "fucking sucks" and berrate you the entire conversation.