Quackery refers to practices or treatments that are considered fraudulent, lacking scientific evidence, or not based on sound medical principles. It often involves healthcare practitioners who make exaggerated claims about their abilities and use questionable methods to treat patients. Quackery can encompass a wide range of activities, from the sale of ineffective remedies to outright fraudulent practices such as false advertising or misrepresentation of qualifications. The term "quack" is often used pejoratively to describe individuals who engage in these types of behaviors.