Why is coffee bean good

Be more specific. Do you mean health benefits/risks? Do you mean economic benefits for growing coffee? For health issues, start here:

http://www.bing.com/search?q=coffee+-+benefits+and+hazards&form=EDGNTC&qs=PF&cvid=adb6d820509b4f9e882792ca2742a561&pq=coffee+-+benefits+and+hazards

For economic benefits of coffee as a crop, enter "coffee - economic benefits" in your browser, hit "search" or "enter" an see what you can find.