Manga is a drawn comic/picture in the typical japanese art.
When a Manga becomes fairly popular, the creators may think about animating the comic
Anime is just short for animation
and I think "Anime"
caught on from the french word "animé", but no-one could bothered using the "é"
so we just said Anime instead.
We don't really call western cartoons, "Anime"
(e.g Ben 10, Johnny Test, Spongebob Squarepants)
We just call them cartoons, because that word is more English.
Manga = Read - Anime = Watch
but besides all that, there is no difference xD