Citrus is a classification of fruits which encompasses many tropical and temperate varieties. These usually are sour and acidic as a result of their high vitamin C content[1], but some are surprisingly sweet.
Examples of citrus include:
The exterior rind is called the zest, the interior rind is called the bitter, the flesh is called the pulp, and the liquid is called the juice. Varieties of citrus are naturally found on every continent except Africa, Antarctica, and Australia. In the United States, the state which produces the most citrus is California and citrus orcharding is a full 7% of that state's gross domestic product.