!5936 翻译完成：5648 补充接口参考的模块说明

Merge pull request !5936 from wusongqing/TR5648V2

en/application-dev/reference/apis/js-apis-backgroundTaskManager.md

-# Background Task Management
+# BackgroundTaskManager
+
+This module provides background task management.
+
+If a service needs to be continued when the application or service module is running in the background (not visible to users), the application or service module can request a transient task or continuous task for delayed suspension based on the service type.
+
+If an application has a task that needs to be continued when the application is switched to the background and can be completed within a short period of time, the application can request a transient task. For example, if a user chooses to clear junk files in the **Files** application and exits the application, the application can request a transient task to complete the cleanup.
+
+If an application has a service that can be intuitively perceived by users and needs to run in the background for a long period of time (for example, music playback in the background), the application can request a continuous task.
 
 > **NOTE**
+>
 > The initial APIs of this module are supported since API version 7. Newly added APIs will be marked with a superscript to indicate their earliest API version.