The solera is a method of aging and blending used almost exclusively in sherry production. Simply put, four rows of barrels are stacked with the youngest wine on top and the oldest wine at the bottom. As an amount of wine is drawn from the bottom barrel, that same amount is replaced from the barrel above, and so on, until the barrel in the top row is replenished with new wine.
Sherry is produced in two styles, Fino or Oloroso:
Fino sherry, which includes Fino, Manzanilla and Amontillado, grows flor while still in barrels. Flor are yeasts that blanket the wine, protecting it from oxidation. A Fino sherry is dry, with alcohol running about 15%.
Sherry of the Oloroso style, which includes the various cream sherries, generally has a higher alcohol content of around 18%.