Coffee is a brewed beverage with a dark, acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia, South Asia and Africa. Green (unroasted) coffee is one of the most traded agricultural commodities in the world. Coffee can have a stimulating effect on humans due to its caffeine content. It is one of the most-consumed beverages in the world.
Coffee has played a crucial role in many societies. The energizing effect of the coffee bean plant is thought to have been discovered in the northeast region of Ethiopia, and the cultivation of coffee first expanded in the Arab world. The earliest credible evidence of coffee drinking appears in the middle of the 15th century, in the Sufi shrines of Yemen in southern Arabia. From the Muslim world, coffee spread to India, Italy, then to the rest of Europe, to Indonesia, and to the Americas. In East Africa and Yemen, it was used in religious ceremonies. As a result, the Ethiopian Church banned its secular consumption, a ban in effect until the reign of Emperor Menelik II of Ethiopia. It was banned in Ottoman Turkey during the 17th century for political reasons, and was associated with rebellious political activities in Europe.
Coffee berries, which contain the coffee seeds or "beans", are produced by several species of small evergreen bush of the genus Coffea. The two most commonly grown are the highly regarded Coffea arabica, and the "robusta" form of the hardier Coffea canephora. The latter is resistant to the devastating coffee leaf rust (Hemileia vastatrix). Once ripe, coffee berries are picked, processed, and dried. The seeds are then roasted to varying degrees, depending on the desired flavor. They are then ground and brewed to create coffee. Coffee can be prepared and presented in a variety of ways.
An important export commodity, coffee was the top agricultural export for twelve countries in 2004, and it was the world's seventh-largest legal agricultural export by value in 2005. Some controversy is associated with coffee cultivation and its impact on the environment. Many studies have examined the relationship between coffee consumption and certain health conditions; whether the overall effects of coffee are ultimately positive or negative has been widely disputed. The method of brewing coffee has been found to be important to its health effects.