...
The Windows Start button and search box are now located in the center at the bottom (instead of bottom far left). If you want it back to the left, in the Windows search box type “alignment”, then click “Controls alignment of the taskbar”. Change Center to Left.
When you click the Windows Start button, it shows pinned apps and recommended files, but you can click the “All” button in the upper right to get to the full alphabetic listing of applications.
In the The bottom lower right corner of that the Start menu , is where you will now find has the Power button to Lock, Sleep, Shutdown, or Restart the computer.
Meet Windows 11: A whole new look - Microsoft Support
...