What's a front freewheel?

There is a use in any system where other things make the crank turn when the rider wants to coast, like a fixed gear where the rider wants to be able to pedal backwards but wants to take a sharp turn without heelstrike, or a tandem out of phase where the stoker wants to not heelstrike... basically anything that involves the crank doing funny things when you want it not to, but can't fix it without doing funny things elsewhere.

Obviously no normal mortal needs this.