This keystroke toggles between show & hide the hidden files:
Cmd ⌘ Shift ⇧ . (that’s a FULL STOP, period character)
Press again to toggle back and forth.
When you reboot your Mac, the hidden files will be hidden. Press the keystroke again to show.
In Terminal.app, paste:
defaults write com.apple.finder AppleShowAllFiles -boolean true; killall Finder
This changes the default setting to show hidden files. And this causes the Finder to restart, so you can see the effect. This new setting persists even after rebooting your Mac.
To revert to hiding again the hidden files, change that
true to a
false and run again in Terminal.