The term "malt" refers to several products of the process: (1) the grains to which this process has been applied, for example malted barley; (2) the sugar, heavy in maltose, derived from such grains, such as the baker's malt used in various cereals; or (3) a product based on malted milk, similar to a malted milkshake (i.e., "malts").
Barley is the most commonly malted grain in part because of its high diastatic power or enzyme content. Also very important is the retention of the grain's husk even after threshing, unlike the bare seeds of threshed wheat or rye. This protects the growing acrospire (developing plant embryo) from damage during malting, which can easily lead to mold growth. It also allows the mash of converted grain to create a filter bed during lautering (see brewing). Other grains may be malted, especially wheat.
Malt is often divided into two categories by brewers: base malts and specialty malts. Base malts have enough diastatic power to convert their own starch and usually that of some amount of starch from unmalted grain, called adjuncts. Specialty malts have little diastatic power; they are used to provide flavor, color, or "body" (viscosity) to the finished beer. Caramel or crystal malts are specialty malts that have been subjected to heat treatment that converts their starches to sugars non-enzymatically. Within these categories are a variety of types distinguished largely by the kilning temperature (see mash ingredients).