As Thurrott.com observes, the new search bar looks and behaves quite like Apple's macOS Spotlight search box, moving results that normally are found from the Start Menu and the Cortana search bar to a central location. The new search UI was discovered by Italian blog Aggiornamenti Lumia.
The search box can be surfaced with the Windows+S shortcut, which opens the search bar in the center of the screen.
After typing in a search, the results are displayed beneath and can be sorted into several filters, including All, Web, Documents, and Settings. Users can search for files, pictures, videos, music, settings, and apps.
Microsoft has only just started building the Redstone 4 Windows 10 release, which should arrive to all users early next year.
Thurrott has provided registry edit instructions for Windows Insiders to activate the immersive search feature in the latest Redstone 4 release.