Coffee tree is a perennial evergreen shrub or small tree belonging to Rubiaceae. Coffee for daily drinking is made from coffee beans with various cooking utensils, and coffee beans refer to the nuts in the fruit of coffee tree, which are baked by appropriate methods. A cup of standard coffee should not taste 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.