Hardcore is a subgenre of punk rock that is thicker, heavier and faster than regular punk. It is not a type of Metal, Techno, or Rap. Hardcore is mostly confused with Metalcore/Melodic Metalcore bands such as Hatebreed or Bring Me The Horizon or hardcore techno. The -core prefix was originally short for Hardcore but now is a random suffix added to anything to make it look more interesting (Easycore, Sadcore etc.). It was invented by L.A. bands like The Germs and Negative Trend in 1976 - 1977 and the bands almost never reached mainstream popularity or even wanted it.
Misfits and early D.R.I are hardcore, while Asking Alexandria and The Prodigy are not.
Powerviolence, emo, skacore, d-beat, and skate punk are subgenres of hardcore.
The most popular hardcore scenes are Los Angeles which was the birthplace of hardcore, New York which is usually more metallic, and D.C. which is usually faster.
Many types of extreme metal like thrash, sludge, and black were mainly influenced by hardcore.
Hardcore is not a subculture. People who listen to hardcore call themselves punks, if anything.
Hardcore music does not mean "any hard music"