Final answer:
The keyboard combination for switching between open windows is Alt + Tab, which displays a thumbnail overlay of all open windows and allows you to cycle through them.
Step-by-step explanation:
The keyboard combination used for switching between open windows is Alt + Tab. When you hold down the Alt key and then press the Tab key, you'll see a small overlay display with thumbnails of all your currently open windows. By continuing to hold the Alt key and pressing the Tab key, you can cycle through the windows, and then release the keys to switch to the selected window.
The other keyboard shortcuts mentioned have different functions: Ctrl + Shift + Esc opens the Task Manager, Windows key + D minimizes all windows to show the desktop, and Ctrl + Alt + Del opens a security options screen.