Pisco is a type of grape brandy, typically colorless or pale yellow, that is the subject of a dispute between Peru and Chile. While both countries claim to make Pisco, there certainly is a port in Peru called Pisco, and production of the spirit was certainly there before 1613, when the will of Pedro Manuel the Greek passed on his pisco-making equipment.
In Peru, Pisco production is strictly regulated. There are a handful of grapes that are divided between Aromatic types (mainly Muscat family) and non-Aromatic varietals. The grapes are distilled, and nothing can be added to change the color, aroma or flavor of the resulting spirit. Aging must take place in a neutral container like glass or stainless steel, then the Pisco must be bottled immediately afterward, at between 76 and 96 proof.
There are a few words you might see on a Peruvian Pisco label: Pure, which means the grapes that make up the Pisco are from one varietal. Aromatic, where the grapes are from the Muscat family. Mosto Verde, where fermentation of the base wine does not finish before the distillation begins. Finally, Acholado will denote a base wine that is a blend of different grapes.
In Chile, the regulations are stricter in some senses and more lenient in others. Chilean Pisco uses Muscat family grapes almost exclusively, which are completely fermented into wine that is about 28 proof. This is then distilled. Some Chilean Piscos are aged in wood, giving them a yellow to brownish color. They must be between 60 and 100 proof.
Pisco is usually pale in color, with a strong aromatic, grape flowery aroma. The texture is more like white rum than unaged brandy. Better producers make a clean, delicate spirit. Chilean Piscos that spend time in a barrel can pick up buttery richness, not unlike Reposado tequila.