The device saves all the data from each hit, namely the animation, path, putter-face angle at impact and throughout the stroke, angle of attack, tempo, impact speed and swing path distance -- in other words, more information than most players would know what to do with.
The included app's well-designed interface shows an animation of your putts and displays a curve indicating the path of your stroke, which can be overlaid against that of a previous, model putt you've chosen.