Safe To Delete Apps.ppkg?

The following's copied and pasted from https://superuser.com/q/1659902.
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1. I must reduce HD disk space. How safe is deleting Apps.ppkg? Its size is 3.6 GB. I must double check because another program file usmt.ppkg MUST NOT be deleted.

2. I read this abstruse explanation of Apps.ppkg, but I don't understand it. Please explain it like I'm 5?

It doesn't clearly advise if deleting is safe. In actuality, the last sentence suggests that deletion ISN'T safe — because if deleting is safe, why would you need make "a backup of the file on external storage"???

 

When you need to free up disk space the simplest way to go about it is to download, install and run Treesize Free. This will display all your files in size order, enabling you to focus on stuff that can make a real difference. I don't know how you come to be focussing on .ppkg files but, by their nature, I think you would be risking the safety of your system if you delete any of those without a full understanding of their function. Also, before deleting anything, you should image your system to safeguard against deleting anything vital.