What does a knowledgeable friend mean by solid-state brewing of pure grain?

Solid state brewing is a brewing process of liquor, and pure grain refers to grain crops as brewing raw materials. In other words, pure grain liquor is a solid-state brewing process of pure grain. Generally, only high-quality liquor will be brewed by solid-state method, because the brewing cycle is relatively long. For example, Jianzhuang wine only uses five kinds of grain as raw materials, and there are no other industrial raw materials, so it is naturally delicious.