The internal gears allow the <hub shell-spokes-and-rim> to turn at a different rate or faster or slower than the gear sprocket turning it.

If there is a pawl to have it pushed out to engage the hubshell and drive it, it needs a return spring to push it out.

like a freewheel/freehub when you apply power the pawls , pushed out by the springs engage ..
when you coast the pawls ride over the ramps and you hear clicking.


Herr Schlumpf's 2 speed crank the pedals turn at a different rate than the chainrings ,

reduction gear cranks turn faster than the chainring , overdrive the chainring turns faster than the cranks.