What are the differences between atomic services and service widgets?

Atomic services are future-oriented user applications provided by HarmonyOS. They are installation-free (installed automatically by the application framework in the background) and can offer one or more convenient services for users. Each atomic service has an independent entry for easy access with a single tap.
A service widget is a set of UI components used to display important information or operations specific to an application, enabling direct access to a desired application service and simplifying user interactions. It is typically integrated into system applications, such as the home screen, and offers basic interactive features such as opening a UI page or sending a message.