Late harvest is a term applied to wines made from grapes left on the vine longer than usual. Late harvest is usually an indication of a sweet dessert wine, such as late harvest Riesling. Late harvest grapes are often more similar to raisins, but have been naturally dehydrated while on the vine.
Botrytis cinerea, or noble rot, is a mold that causes grapes to lose nearly all of their water content.
Wines made from botrytis-affected grapes are generally very sweet.