Original: The wine produced is then fortified with the addition of a Brandy (distilled grape spirits) known as Aguardente in order to stop the fermentation, leaving residual sugar in the wine, and to boost the alcohol content.
Simplified: The wine produced is then fortified with the addition of a Brandy (distilled grape spirits). This is done to stop the fermentation leaving residual sugar in the wine and to increase the alcohol content.