switch between app's open windows? (Was CMD "<" )

Good morning!

Here's a new MacBook Air running ventura newest OS.

How please can I set the keyboard shortcut to switch between the frontmost app's active/open windows?

This used to be very accessible, CMD - "<".

Now, and on this specific Mac, it's not. The Macbook belongs to my wife, and her previous computer (MBA 2010) had this key screwed up too, so it probably is a inherited configuration flaw...

Where's the place to 1) look up the short-cut and 2) alter it to my wife's taste?

Sidenote: Is there a place where I can look up the meaning of a specific keyboard-shortcut, like "What does cmd-< (or, haha, CMD-C) do?"