Musical instruments generally belong to the general category of "other industries". Category is one of the most important attributes of goods, such as men's wear, women's wear, shoes, skin care, electronics and so on. All belong to the category, which is equivalent to selling what products. Categories will also be divided into first-class categories and second-class categories, and some will be extended to fifth or even sixth-class categories. For example, clothing is a first-class category, divided into men's wear, women's wear and children's wear, which can be defined as a second-class category. The next category is the detailed definition and division of men's and women's clothes.