What is manga animation?

Manga is similar to an American comic book, but in black & white, thicker, and more stylized (exaggerated). If you compare an American comic book and manga, comic books are generally thin like a magazine, running about 32 pages, while a manga is around a hundred pages (for 1 manga book) in length!

In page count, Manga is quite similar to graphic novels, which are often just collections of the ongoing American comics. But unlike American graphic novels, which are usually just a collection of monthly comics in a single unified story or story arc, Manga books are often apart of an even bigger story and a complete Manga storyline can run thousands of pages.

Anime is an animated version of a manga series. Once a manga gets very popular, certain people look at the manga and see if it's good. The manga must qualify or it will not become an anime. Once it's approved, they find voice actors, make the animation, other stuff.... Some paraphrasing is made as well. Before it broadcasts on tv a contract must be made.

- An improved answer by Yukini