A paper bag is a type of container made from thin, flexible sheets of material (usually paper) that are folded and sealed together to create an enclosed space. These bags can come in various sizes and shapes, but they all serve the same basic purpose - holding items such as groceries or other goods. The term "paper bag" is also used figuratively to describe a person's facial expression that indicates anxiety, nervousness, fear, or embarrassment; for example, if someone is caught doing something wrong and their face turns red like a paper bag over their head, it means they are feeling ashamed.