Windows 10 can use tablet mode for small devices like smartphones and small tablets. It can be set to do that automatically or to just remember which mode you used last.
Tablet mode is supposed to make it easier to use your fingers instead of a mouse and physical keyboard. Your apps may not be ready for true mouseless work.

If you want to use Tablet mode when Windows 10 does not automatically switch -
Click the Action Center icon, You may not notice a difference immediately if you have a program open full screen.
New icons at top left of the screen:
Right click on the Taskbar.The choice 'Show all notification icons' will show only the icons that show in Desktop mode. Any icons on the palette of notification icons will still be there.