Back in '84, it referred to a nascent movement, a little clump of bands who were making "emotional hardcore" or "emocore." Now it refers to a youth fashion. Here's the wiki, which is pretty much accurate.
Interesting to look at the graphs and note the huge spike and almost immediate decline of searches having to do with deaths - Anna Nicole Smith, Virginia Tech, and Pavorrati, while the, I guess, nicer searches stayed more or less consistent.