Plantains are a member of the banana family. They are a starchy, low in sugar  variety that is cooked before serving as it is unsuitable raw. It is used in many savory dishes somewhat like a potato would be used and is very popular in Western Africa and the Caribbean countries. It is usually fried or baked. It's such a versatile fruit, yet it is so misunderstood. And while most people think it looks like an ugly banana, it is really much, much more.

The plantain is the only fruit that can be used at all stages of ripeness, (green, yellow and black) and it has distinct and delicious flavor at all stages. While the plantain is a fruit, it is not eaten raw like any other fruit but is treated more like a vegetable and served fried, baked, mashed, sautéed, stuffed, or even micro-waved.

The versatile plantain can be used to create enticing appetizers, satisfying entrées or tempting desserts. And, because it's usable at all stages of ripeness, the plantain has almost no waste. The main difference between a banana and a plantain is moisture content. The plantain averages about 65% moisture content and the banana averages about 83% moisture content. Since hydrolysis, the process by which starches are converted to sugars, acts fastest in fruit of higher moisture content it converts starches to sugars faster in bananas than it does in plantains. A banana is ready to eat when the skin is yellow whereas a plantain is not ready to eat "out of hand" until hydrolysis has progressed to the point where the skin is almost black.

Good source of plantain information:
http://www.turbana.com/

http://www.turbana.com/planrcpe.htm