Sake is a Japanese alcoholic beverage made of rice, water, koji and yeast. Sake is also referred to in English as “Japanese rice wine.” Sake is produced by multiple fermentation of rice, which actually is similar to how beer is produced. Although sake is called rice wine it is more like a beer in the way it is produced.

Junmai-Shu:
Junmaishu refers to pure sake, pure in the sense that no adjuncts (starches or sugars other than
rice added to the fermenting mixture) were used, and that no brewer’s
alcohol was added either.  Junmai-shu, like Honzojo-shu, must be made
with rice with a Seimai Buai (degree of milling) of at least 70%.

Honjozo-Shu:
Honjozo is sake wherein a small amount of distilled pure alcohol is added to smoothen and lighten the flavor, and to make the sake a bit more fragrant. Honjozo-shu, like Junmai-shu, must be made with rice with a Seimai Buai (degree of milling) of at least 70%.

Ginjo-Shu:
This is sake made with rice that has been polished (highly milled rice, with or without alcohol added) so that no more than 60% of its original size remains. This removes things like fats and proteins and other things that impede fermentation and cause
off-flavors.

Daiginjo-Shu:
Daiginjo-shu is ginjo-shu made with rice polished even more (highly milled rice, with/without added alcohol), so that no  more than 50% of the original size of the grain remains. Note that the term junmai can be added in front of either ginjo or daiginjo if no alcohol is added to result in either junmai ginjo or junmai daiginjo. However, distilled alcohol often is added in small amounts to ginjo and daiginjo to heighten the aroma, not to increase volume, so a junmai daiginjo without added alcohol is not necessarily a better product than daiginjo.