The "End Task" button cannot terminate system processes such as File Explorer, for that you will still have to go through the Task Manager which kind of makes sense.

To close this program, simply left click once on the program name and then click on the End Task button. If the program is in the Running state, the program will just close as if you clicked on ...

Windows 11 allows you to force quit unresponsive apps using the Task Manager. However, there's an alternative method that's even faster.

If a program is running in the background on your Windows 11/10 PC & you can see it on Taskbar or Task Manager but is not visible on your desktop screen, see this post.