Feathering is just the same as on an aeroplane propeller, you change the pitch of the blades to suit the circumstances of the moment.
There's a middling sized wind generator a couple of hundred yards behind me, and you often see the blades are feathered and not rotating, much of the time when winds are too high.
Interestingly, the generator is actually controlled from Ireland, not even from the UK - and if the power isn't needed, they feather the prop and shut it down.
