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, noble rot, is a mold that causes grapes to lose nearly all of their water content. Wines made from botrytis-affected grapes are generally extremely sweet. Sauternes, such as Chateau d'Yquem, and many Tokaji wines are made from botrytis-affected grapes. Late harvest wines are made from grapes that have not necessarily been affected by botrytis, although the end result is often similar.
For German late harvest wines see spätlese, auslese, beerenauslese and trockenbeerenauslese, and for wines frozen on the vine see icewine.