A bag is a bag-like container used to pack items. It is usually made from sustainable materials such as paper, plastic or composite materials, with certain durability and protective properties. Bags can come in different shapes and sizes to suit different packaging needs. Common types of packaging bags include plastic bags, paper bags, composite bags and so on. They can have different sealing methods, such as self-sealing, zipper, heat sealing, etc., to ensure the safety and tightness of the packaged items. Packaging bags usually have a certain load-bearing capacity and can carry a variety of items, such as food, medicine, cosmetics, clothing and so on. They can be personalized through printing, stamping, labeling and other ways to meet the needs of different brands, and play a role in publicity and promotion.