What is System Junk and can I delete it?

Your Mac does not require any anti virus or so called “cleaning apps” in fact they can slow down your Mac or completely ruin that install of macOS.

Avoid opening or downloading items from email messages and websites unless you are certain that they come from a legitimate, trusted source. If you’re uncertain about the source, delete the item.

Please Read

https://discussions.apple.com/docs/DOC-8841

Hope that helps and have a nice day

thank-you I did not know about that

I've done a lot of testing on these mac cleaning apps using virtual machines and there mostly all junk that damage the system and slow down the mac

if you want to free up space use this guide

How to free up storage space on your Mac - Apple Support

it is not safe

uninstall Clean my mac

CleanMyMac 3: Clean Up Your Mac with Best Mac Cleaner. Clean My Mac 3

I am saying that it is not safe

it is not recommended by apple

what do you mean by Tech Talk