Sake is brewed -- and not distilled -- from rice. The alcohol content is initially about 20 percent, but this is usually watered down to about 16 percent, which is just a tad more than most wine. But sake is closer to beer than wine, at least in terms of how it is made.
Sake is brewed from a grain just as beer is, and the processes have some similarities. Both barley (beer) and rice (sake) contain only starches, not the sugars that are to be converted by the yeast cells into carbon dioxide and alcohol. In beer, this starch-to-sugar conversion takes place with the help of malting the barley, a step in which enzymes are created. In sake, the husk-less rice cannot be malted, so the enzymes are contributed with the help of a mold known as koji-kin.
One thing that makes sake brewing different from beer brewing (and unique in all the world) is that this starch-to-sugar conversion and the conversion of that sugar to alcohol and carbon dioxide take place simultaneously, in the same tank, and not sequentially as in barley-based beverages.