Base and specialty 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 but provide flavor, color, or “body” (viscosity) to the finished beer. Specialty caramel or crystal malts have been subjected to heat treatment to convert their starches to sugars nonenzymatically. Within these categories is a variety of types distinguished largely by the kilning temperature.
Mash ingredients, mash bill, or grain bill are the materials that brewers use to produce the wort that they then ferment into alcohol. Mashing is the act of creating and extracting fermentable and non-fermentable sugars and flavor components from grain by steeping it in hot water, and then letting it rest at specific temperature ranges to activate naturally occurring enzymes in the grain that convert starches to sugars.