Sherry is a fortified wine, made in and around the town of Jerez, Spain. Hence in Spanish it is called "Vino de Jerez;" in fact, the word "sherry" is an Anglicized version of the town's name. According to Spanish law, Sherry must come from the small triangular area of the province of Cádiz between Jerez, Sanlúcar de Barrameda, and El Puerto de Santa María. In earlier times Sherry was known as sack (a rendering of the Spanish saca, meaning a removal from the solera), or more fully as Sherris sack.
Sherry differs from other wines because of how it is treated after fermentation. After fermentation is complete, it is fortified with brandy. Because the fortification takes place after fermentation, all natural sherries are dry; any sweetness is applied later. In contrast, port wine is fortified halfway through fermentation, stopping fermentation so not all the sugars are allowed to turn into alcohol and so leaving a sweet wine.