basically, you get one of those every other combat (and it regens after an extended rest) usable once per combat, it gives you another standard action to use however you will during your turn
yeah. Failures, especially trained failures on skills are not actually failures of your own talents usually
so, a low stealth roll from you, Mr. sneaky, is not that you suck at stealth, but that you don't accomplish your objective /despite/ being good at stealth