Part of macOS
SpotlightSpotlight search window
○ Leave it
Shows the Spotlight search window.
What it is
Draws Spotlight’s search field and results when you press ⌘Space.
If you stop it
macOS starts it again straight away. Leave it.
The verdict
○ Leave it. Part of macOS, or something that starts again by itself. You never need to close these.
In Activity Monitor
SpotlightSpotlightHelper
From Procession’s guide, in the words the app shows.