Mouse Clicking Causes a New Additional Desktop (Inner) Border ?

[Robert4]

Hello,

Not sure if I ever saw this before. Probably always did the following, but I never noticed.

Very hard to describe.

If I do a left button click on the Mouse, it seems the desktop displays an "inner border image".
Clicking agin goes back to "normal".

Has a new, different tone of the normal blue borders a short distance from the edges.

What am I seeing, please ?

Bob

 

[galad]

Tip: How to turn off macOS Sonoma's click to reveal desktop

For macOS Sonoma, Apple changed the Mac so that clicking on the desktop activates Expose and hides all your apps. Fortunately, you can stop it — albeit with a workaround.

appleinsider.com