Despite being a manga inspired/influenced/style artist, I'd imagine a large percentage of people I know don't really know what manga is, let alone understanding the differences between it an anime. I don't think the answer is a simple 'one term fits all scenarios' sentence, but I thought I'd try my best at summing it up with a little help from Wikipedia.
What is the difference between Anime and Manga?
Anime is a term to describe animation created in Japan. In the west, the term is “anime” is defined as a style and genre of animation typically originating in Japan, and can often feature detailed, colorful imagery, unique, in-depth characters and action orientated plot lines either set in the past, present, futre or often within a fantasy setting. The meaning of the term ‘anime’ can sometimes vary depending on the context it’s used in.
Manga is a term to describe comics created in Japan, or produced by Japanese Manga Ka (artists), primarily for a Japanese audience. The style was developed in Japan though the mid to late 19th century with heavy influenced from western and american comics combined with the long and complex history of Japanese art and wood-block prints. In the western world, the term is often defined as a style of drawing originating in Japan and many western artists have adopted this style and refer to themselves as Manga artists.
So we could summarize:
Anime = animation in a typical Japanese cartoon style. Often in full Colour.
Manga = comics in a typical Japanese cartoon style. Often in black & white and with grey tones.