What is the difference between closing an app and force quitting/killing an app?

I don't understand the difference between closing an app and killing it from the user point if view.

As far as I know if I want to close an app I will proceed like explained here https://support.apple.com/en-us/HT201330

But if I want to kill the app, how me, as a user, can do this? I know for android if you search in settings the app there is a button called force stop.

Also, for example, when receiving Background Push Notification there is this concept of force quitting an app
https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app
Usually, when you close, you have opportunity to save data, conext…

When app is killed, that may not be possible.
But can the user kill an app? how can I kill the app?
Accepted Answer
Yes you can, but it is not recommended to do so.

See this:
https ://www.imore. com/how-force-quit-apps-iphone-ipad
or
https: //www.ipho  neha  cks.  com/2017/11/how-to-kill-force-quit-apps-iphone-x.html
What is the difference between closing an app and force quitting/killing an app?
 
 
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