NG-Lightning is an open-source library designed to bring the Lightning Design System to Angular applications. It provides a suite of Angular components that enable developers to easily implement and maintain user interfaces that are consistent with the Salesforce Lightning Experience. By leveraging components from the Lightning Design System, NG-Lightning ensures that Angular applications have a modern and cohesive look and feel while reducing the amount of custom code required. The library is particularly useful for developers who are building applications on the Salesforce platform and need to adhere to its UI standards.