Ice wine (or in German, Eiswein) is a specific style of sweet dessert wine produced from grapes that have been frozen while still hanging on the vine.
Different from the grapes used for other styles of dessert wines, such as; Sauternes, Tokaji, or Trockenbeerenauslese. The grape for ice wine should not greatly be affected by Botrytis or noble rot at harvest time. Rather healthy grapes stay ripening on the vine until it possibly snows and then it is time to quickly harvest our ice wine.
The discovery of Ice Wine was like all good things - accidental. Due to a cooler than normal summer and an exceptionally cold winter in 1794, wine producers in Franconia - Germany, with no other choice, created an Ice Wine by pressing juice from frozen grapes.

 

They were amazed by the high sugar concentration in the pressed juice. It is believed around the mid 1800's, when 'Ice Wine' was started being made around the globe.
Grapes are now left on the vine well into the winter months. The resulting freezing and thawing of the grapes dehydrates and concentrates the sugars and acids inside the grapes, thereby intensifying the flavours and adding complexity. This juice is then fermented very slowly for several months, stopping naturally. Genuine Ice Wine must be naturally produced; no artificial freezing is permitted.
The Ice Wine harvest is done entirely by hand, and commences once the temperature drops below -10°C and the grapes have frozen naturally on the vines. As the nearly frozen grapes are pressed, the water portion of the juice remains within the grape skins in the form of ice crystals. A tiny but precious volume of highly concentrated juice is released.
The juice from Ice Wine grapes is about one-fifth the amount you would normally get if you pressed unfrozen grapes. To put it another way, a typical vine will normally produce sufficient grapes to make a bottle of wine; but frozen grapes will produce only one glass of Ice Wine. This helps explains the difference in price between the two.
Typical grapes used include: Riesling, Vidal Blanc and interestingly Cabernet Franc. A Cabernet Franc Ice-Wine results in a sweet wine with a light pink colour - enjoy.