Background Action is only supported on the client-side (this is why the template is in the Display Actions category).
As the name implies, it runs in the background (asynchronously) without blocking the other actions. In effect it defines a lower-priority process which will execute only when the client is free from other chores.
Since the Background Action aims to avoid blocking of other actions, it's <Done> exit is fired immediately after it is invoked, rather than when it's processing is complete, so in most cases, client-side modelling depending on this <Done> exit will execute before the Background Action itself executes. BTW the Display actions Dialog/Popup/Pop-in are also asynchronous, firing <Done> as soon as the open.
A Control trigger will be added to the template in the next version.
If you want to implement similar asynchronous behavior on the server-side, use a Miscellaneous/Timer, which can be configured to perform a single delayed execution, as explained in the comment included in the Timer template.
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