What keyboard shortcut lets me cycle through my open windows on my MacBook?

I have a MacBook but before this I used Windows PCs and laptops. Alt+Tab in Windows lets me flip through all my open windows / applications. How do I do that on a Mac? And don't tell me Command+Tab, because that doesn't work to bring up the other Firefox window I have open. And neither does Ctrl+Shift+F4. And how to I flip between tabs in Firefox? Windows lets me do it with Ctrl+Tab or Ctrl+1 (or 2 or 3 ,etc).