Many people collaborated and pick up special good grapes from fully ripened ones. Anyway, it is special wine. It is expensive but very sweet. I recommend you to have it for dessert. Eiswein Wine made from grapes left until December or January, then harvested when it is frozen.
Water is removed by squeezing grapes as they kept to be frozen.
The sugar content is very high. I visited Wine Center in Trier near the Mosel on the very cold day. It is made from dried grapes like raisin. It is very sweet and expensive.