Otaku Dictionary: Manga

Noun
1) A particular style of comics that originated in Japan. Important characteristics include large eyes on the females (and sometimes the males, too, depending on the genre), and uncommon hair styles/colors. The art overall just tends to be prettier, too. Unlike comics in the West, manga is read by anyone of any age and there are several different types of genres.
Many anime originates as a manga, but there are also anime that have been anime and then given a manga (K), and light novels (Haruhi, Durarara), video games (Akaya Akashiya Ayakashi, to name an obscure one), and recently even series of Vocaloid songs (Kagerou Daze, Shuuen No Shiori), that have received the manga treatment.
And its almost always read right to left. If it is not, it is most likely not authentic manga.
And, you read manga, you watch anime