Wha exactly a "pending" trigger Notification is?

[Spasp]

Hello, and thanks for your amazing work for this package!
I would like to clear out what a "pending" trigger notification is.
In a case which:

• a trigger notification is not displayed to the user (ex. low battery)
• and the triggering time has passed,
  it is still considered as a "pending" triggerNotification or it is cleared out from the system?

P.S I have searched the documents, issues and I could't find an answer, If I missed something I am very sorry, I am quite new in these stuff.

Thanks!