What is cosplay?
Here's the answer to those unfamiliar with manga, anime and other japanesery.
Cosplay is a portmanteau word of 'costume' and 'playing'. In practice, this involves reproducing the dressing attire worn by, in most cases, manga or anime characters (Dragon Ball Z, Sailormoon, Chobits, ...) or videogame characters (Final Fantasy, Street Fighter, ...) and 'parade' around during Japanese culture conventions being held here and there in the world, and also in the United States. Cosplay is for many people THE most important thing to see in these conventions.
Please notice that, contrary to popular belief, the phenomenon hasn't taken root in Japan! Indeed it was started by... the Americans, who were the first to implement this idea during sci-fi conventions, in which you could see fans dressed up as Star Trek crew members or Star Wars Stormtroopers. Japanese people then adopted the tendency to their own anime and manga works, and later named it "cosplay".
Good to be known as well: in most cases, not only the costume, but also the character's attitude have to be reproduced.
Even though manga and anime contributed to the explosion of the phenomenon, American and European works are also represented through cosplay: during conventions, one can easily find costumes taken from blockbuster movies such as Lord of the Rings, or from comics such as the X-Men. Europe isn't forgotten either, with the inevitable Harry Potter characters or even Asterix.