Introduction
Gackt Camui joined the band Malice Mizer in 1995, and with them rose in fame in the Japanese Visual Kei scene. In 1999, he started his solo career and has since released 9 albums and 27 singles. His music has been used in several anime series and video games. He co-starred and co-wrote the 2003 film Moon Child, appeared in the NHK drama Furin Kazan, and is slated to appear in the 2009 American film Bunraku.
...Frankly, I'm not very good with introductions, though I'll work on making this less awful. XD If you'd like to learn the basics about Gackt, I suggest checking out the profile on his official site (although it's largely Engrish). I hesitate to suggest Wikipedia, but it does have some information — just take it with a grain of salt.