A stain is a mark or discoloration that appears on a surface, often caused by the absorption of a substance. Common examples include food spills, ink, or dirt that can affect materials like fabric, wood, or walls. Stains can be temporary or permanent, depending on the material and the cleaning methods used. Removing a stain typically involves using cleaning agents or techniques tailored to the specific type of stain and surface. For instance, bleach may be effective on white fabrics, while vinegar can help lift stains from carpets. Prompt action often improves the chances of complete removal.