1# Background Services (Stage Model) 2 3 4The stage model uses ServiceExtensionAbility to provide background services. A system application can implement a background service and provide external capabilities. For example, if system application A implements a background service, third-party application B can communicate with A by connecting to A's background service. 5 6 7For details about ServiceExtensionAbility, see [Background Service Development](serviceextensionability.md). 8