"We hope that secret boards will make Pinterest even more useful. You can use secret boards to keep track of holiday gifts, plan a special event, or work on a project you aren’t yet ready to share with the rest of the world. You can keep your secret boards to yourself or invite family and friends to pin with you "Or maybe if you had weird stalkers this would be a perfect way to pin something without them seeing...just saying.
To access them you scroll down your boards on your profile page and you'll find them at the bottom...now you only get three secret boards so choose wisely!! :)