Attention: Board Notes does nothing useful in and of itself! It is is a companion app to Board that is available exclusively for iPad. You dont need this app if you dont have Board.
Board Notes allows you to connect to whiteboards created by Board near you.
You can then interact with the whiteboard by writing on and throwing sticky-notes from your device to the whiteboard, where they can be organized and modified.
This is especially useful for collaborative brainstorming sessions in education, project management, creative applications and pretty much anything else you can think of.