Sherry is made in a unique way using the solera system, which blends fractional shares of young wine from oak barrels with older, more mature wines. Sherry has no vintage date because it is blended from a variety of years. Rare, old sherries can contain wine that dates back 25 to 50 years or more, the date the solera was begun. If a bottle has a date on it, it probably refers to the date the company was founded.
Most sherries begin with the Palomino grape, which enjoys a generally mild climate in and around the triad of towns known as the "Sherry Triangle" and grows in white, limestone and clay soils that look like beach sand. The Pedro Ximenez type of sweet sherry comes from the Pedro Ximenez grape.
Sherry is a "fortified" wine, which means that distilled, neutral spirits are used to fortify the sherry. The added liquor means that the final sherry will be 16 to 20 percent alcohol (higher than table wines) and that it will have a longer shelf life than table wines.