The backbeat tells you where; the ghost notes tell you how. A ghost note is a snare hit so soft it's almost subliminal — a whisper between the loud snares on 2 and 4. They fill the space, give the groove its forward motion, and define the genre.
If you take the ghost notes out of a funk groove, it stops being funk. They're not decoration; they're structural.
Exercises
Funk Groove with Ghost Notes
Snare on beat 2 and beat 4 is loud (the backbeat). All other snare hits are ghost notes — barely audible, played from your fingers. Aim for a 4-to-1 ratio between accented and ghosted snare. The groove should feel like a whisper interrupted by two slaps.