Any sort of rhythm depends on there being a gap in the sound. Otherwise it would be just a constant tone. It’s easy to notice the notes that make up the sounds, but next time you hear the beating of a drum try to notice the space of time between the notes.
A groove can be made by one or many instruments. The same silence between notes creates a rhythmic pattern for each instrument, and the synchronized combination creates the overall groove. Even though it’s easier to notice the different sounds, the different silences are just as much a part of the groove.