Many factors affect flavor.

With hundreds of chemical and organic compounds contained in the tiny brown bean (and more being discovered constantly), and with many factors influencing which compounds you taste, this complexity makes sense. The genetics of the particular coffee plant influence its flavor, as does the soil in which it grows and the kind of water it receives. After harvesting, such factors as fermentation practices and other variables of processing add to the coffee's flavor profile. Additionally, even within the same variety, every coffee plant reacts differently to the same factors, and many coffees are blends of local groupings of plants. Or even different regions or countries.