Coffee tree is a perennial evergreen shrub or small tree of Rubiaceae. Coffee for daily drinking is made of coffee beans with various cookers. Coffee beans refer to nuts in the fruit of coffee trees, which are baked in an appropriate way. A cup of standard coffee should not be bitter. A qualified barista will carefully carry out every step when making coffee, and finally the coffee presented to the guests will show different degrees of sweetness, acidity and mellow taste.