There are two basic types of sake:
futsū-shu (普通酒) and tokutei meishō-shu (特定名称酒).
Futsū-shu, "ordinary sake," is the equivalent of table wine and accounts for the majority of sake produced.
Tokutei meishō-shu, "special designation sake," refers to premium sakes distinguished by the degree to which the rice is polished and the added percentage of brewer's alcohol or the absence of such additives.
Honjōzō-shu (本醸造酒), in which a slight amount of brewer's alcohol is added to the sake before pressing, in order to extract extra flavors and aromas from the mash. This term was created in the late 1960s to distinguish it, a premium sake, from cheaply made liquors to which large amounts of distilled alcohol were added simply to increase volume. Sake with this designation must be made with no more than 116 liters of pure alcohol added for every 1,000 kilograms of rice.
Junmai-shu (純米酒), "pure rice sake," made from only rice, water and kōji, with no brewer's alcohol or other additives. Before 2004, the Japanese government mandated that junmai-shu must be made from rice polished down to 70% or less of its original weight, but that restriction has been removed.
Ginjō-shu (吟醸酒), made from rice polished to 60% or less of its original weight. Sake made from rice polished to 50% or lower is called daiginjō-shu (大吟醸酒).
The term junmai can be added to ginjō or daiginjō, resulting in junmai ginjō and junmai daiginjō. However, as distilled alcohol is added in small amounts to ginjō and daiginjō to heighten the aroma, not to increase volume, a junmai daiginjō is not necessarily a better product than a daiginjō made with brewer's alcohol.
In addition to "ordinary" sake and the special designations, there are many more types of sake.
Nigori (or nigorizake) is a variety of sake. Its name translates roughly to "cloudy" due to its appearance. Normal sake is usually filtered to remove grain solids left behind after the fermentation process, however nigori sake remains unfiltered, resulting in a far cloudier drink.
Nigori sake is generally the sweetest of all sakes, with a fruity scent and a mild flavor, making a great drink to complement spicy foods or as a dessert wine. Before serving, the bottle must be shaken properly to mix the sediments with the sake, to obtain the full range of flavor and its "signature look". It is advised that it be served well-chilled, storing it in an ice bucket to keep it from warming up between servings. It is also recommended, as with most sakes, to consume the entire bottle once opened as it begins to oxidize, altering its flavor.