Manga means Comics or Drawings in Japanese. There really isn't any comparison to the American Comics. The content of Manga is much more diverse. Manly focusing attention on the 15 and older population.
Did you know about the different styles of Manga?
Shojo means young woman or girl in Japanese. When seeing Shojo on Manga, this means that this particular type of comic is directed towards the female audience.
Shonen means young man or boy in Japanese.Of course, like Shojo, seeing Shonen on Manga means that comic is primarily for young men. The art isn't drastically different. However, the body is enhanced, and the faces are usually more define.
I just started getting into Manga. So I don't have many sites. But bare with me, I'll get more for you!