How do I take a screenshot on Windows 11 and Mac, including just part of the screen?

I know Print Screen exists but it seems to do nothing on my new laptop, and on my Mac I keep taking pictures of the whole desktop when I only want one window. What are the actual shortcuts?

Windows 11

• Win + Shift + S: opens the Snipping Tool overlay. Drag a rectangle, or pick window / full screen from the small toolbar. The image goes to the clipboard and is also saved to Pictures\Screenshots.
• Win + PrtScn: full screen, saved straight to Pictures\Screenshots.
• PrtScn alone: copies the full screen to the clipboard (paste it somewhere). On many laptops it is on a function key, so you may need Fn + PrtScn. You can also set PrtScn to open the Snipping Tool in Settings, under Accessibility, Keyboard.
• Alt + PrtScn: just the active window, to the clipboard.
• Win + G: the Game Bar, for capturing games.

Mac

• Cmd + Shift + 3: full screen.
• Cmd + Shift + 4: drag to select a region. Press Space after that and the cursor becomes a camera: click a window to capture just that window, with a nice shadow.
• Cmd + Shift + 5: the toolbar with all options, including screen recording and where to save.
• Hold Ctrl with any of these to copy to the clipboard instead of saving a file on the desktop.

Phones, since someone will ask: iPhone is side button + volume up; most Androids are power + volume down.