Malt is a cereal grain (usually barley) that has been steeped in water and allowed to germinate. The germination process produces enzymes that convert the starches in the grain into sugars. Mash is the process of mixing the malted grain with hot water to extract the sugars. The resulting liquid is called wort. Wort is then boiled with hops to produce beer.
Malting and mashing are essential steps in the brewing process. They convert the starches in the grain into sugars, which are then fermented by yeast to produce alcohol. Malt and mash also contribute to the flavor and aroma of beer.