Hot Corners is a feature of macOS that allows you to perform functions when the cursor is moved to one of the four corners of your screen. You can trigger Mission Control, put your Mac to sleep, run Launchpad and other functions. You can also set Hot Corners to only trigger if you have modifier keys pressed.
In the past i have only used one corner because it bugged me starting stuff just because i waved my mouse to close to the corner, BUT now you have have showed the OPTION or COMMAND key extra tip = now thats helpful!!
Another "THANK YOU GARY!". For years I've been plagued by my screen suddenly disappearing when my cursor runs over something I'm not conscious of. There's a "do nothing dash" in hot corners that cured this annoyance in about 10 seconds! Thank you Gary!