ng-bootstrap is a project that provides ready-made Angular component wrappers for Bootstrap's components. It solves all the data binding and event-oriented aspects associated with using Bootstrap's vanilla jQuery components, while still looking and functioning identically. However, ng-bootstrap only provides the Angular component wrappers for generating Bootstrap components and does not import any Sass for styling components; we still have to do that ourselves.

The ngb-accordion and ngb-panel Angular components are adaptations of Bootstrap's collapsible group and collapsible card components, specifically tailored for Angular. The activeIds attribute on the component tells the ngb-accordion component which ngb-panel should be active by default. The title attribute provides the title that is displayed on the ngb-panel, while the ngbPanelContent directive on the template inside it contains the content that will be displayed when the panel is active. The ngb-accordion component automatically tracks and updates the state of these panels for us when we click on it.