The term "manga" is used for Japanese comic books. That said, manga and American comics are very different. Manga usually comes in phone book sized anthologies, printed weekly, bi-monthly or monthly. 40% of all publications in Japan are manga and there are a wide variety of subjects. It is not uncommon to see a young girl sitting on a train reading shoujo (girl-specific) manga, sitting next to a business man reading adult manga. It is a very wide and diverse media, and now some American comic book companies are translating these works and making them available in the United States. The products of this fan following can be found here, in Arts/Comics/Manga.
More information