It is short for "costume play" and it entails dressing up in very fancy clothing, often animation related. Japanese animation, manga, and video games are the inspiration for most cosplay. It's a very social activity that friends can do together. Animation and comic book conventions around the world are common meeting places for cosplayers. And apparently, Everland is too!
If you are any of these cosplayers, thanks again for letting me put your picture up! When I told some of these cosplayers about this blog (Korea & Animation), they corrected me that they were dressed as Japanese animation characters, not Korean characters. This makes me realize what a good job Japanese artists do at creating characters that we want to be just like. I think we in other parts of the world, including here in Korea, should work hard to create those kinds of characters, too. After all, look how much fun it is!