There are many types of sake being made today. A proper understanding of sake begins with learning sake grades. In Japan, sake is officially categorized based on the degree rice is milled, as well as, if neutral spirit was added or not.
Sake, or rice wine, obviously relies heavily on rice as an ingredient. The more the rice is polished (milled), the fruitier and lighter the resulting sake will become.
There are nine major sake types. The lowest quality grade is futsushu. This is basically table sake. Futsushu does not have a legal minimum of rice polishing. A large amount of neutral spirit can be added, and sugar and other additives are allowed too.
Premium sake is officially called tokutei meisho shu (toh kuu tay may soo shuu). These sakes have stricter requirements. Most of the sake exported from Japan will fit into this group.
Junmai means “pure rice” and contains no added alcohol. There are four types of Junmai sake: Junmai, Tokubetsu Junmai, Junmai Ginjo, and Junmai Daiginjo. Each of these requires progressively more milling for the rice used. Regular Junmai has no minimum polishing amount. Junmai Ginjo must use rice polished at least to 60% (40% removed). And Junmai Daiginjo requires at least 50% of the rice to be polished away.
Honjozo, Tokubetsu Honjozo, Ginjo, and Daiginjo are the other premium sake grades. They are parallel in quality with the Junmai sakes, but allow a small amount of added neutral spirit. These sakes tend to be lighter and more aromatic than the equivalent Junmai.
Honjozo has a minimum milling amount of 70%, Ginjo requires rice to have been milled to 60% (remaining) or more. And finally, Daiginjo, like Junmai Daiginjo, requires that at least half of the rice is polished.