As a generic grouping component for web content, Panel has features such as toggling and custom content. A basic definition of the Panel would be as follows:

<p-panel header="PrimeNG">
  PrimeNG is a collection of rich UI components for Angular.
  PrimeNG is a sibling of the popular JavaServer Faces Component Suite,  
  PrimeFaces.
  All widgets are open source and free to use under MIT License.
  PrimeNG is developed by PrimeTek Informatics, a company with years of 
  expertise in developing open source UI components.
</p-panel>

The preceding definition of the Panel will display PrimeNG details inside the container as shown in the following screenshot:

The Panel is going to be more user friendly, with toggleable (toggleable="true") and custom header content features. The toggleable feature defines the content as either expanded or collapsed. The initial state of the Panel content (expanded or collapsed) defined with the collapsed attribute; by default, the content section will be expanded, whereas the customized header and footer is defined through the p-header and p-footer tags which accepts text, images, icons, and many more. For example, the customized header with list of PrimeNG resources in the form of drop-down would be as follows:

We can catch the user actions before toggling and after toggling using onBeforeToggle and onAfterToggle callbacks.