A collapsible panel is a user interface element that allows content to be expanded or collapsed, making it easier to manage large amounts of information. When a user clicks on the panel's header, it either reveals or hides the content inside, helping to keep the interface clean and organized. This feature is commonly used in websites and applications to enhance user experience. These panels are often implemented using programming languages like HTML, CSS, and JavaScript. They can be found in various contexts, such as FAQs, menus, and dashboards, allowing users to focus on the information they need without being overwhelmed by excess content.