Exercise! - The giggly machine

So, recently, I turned a corner at the gym and saw a gentleman on the "giggly machine." My mouth gaped into an inappropriate stare, and he glared back at me (which was certainly appropriate considering my reaction). I simply had no idea what he was doing. There is this contraption at my gym, and it giggles people. Maybe vibrate is the more appropriate term? But, vibrate simply doesn't express the intensity of this odd machine. People stand on this platform, and it vibrates. I tried it today, but it's benefits (if it has any) were clearly lost on me.

Does anyone know what this contraption is? What is it supposed to do? Besides make me stare uncomfortably at whoever is using it...

I believe that it has the ability to increase bone density. I know a few people here have mentioned them. They are vibration machines, although I don't know the official word for them.

It doesn't do much for anything just standing on the platform. It is supposed to have a small amount of benefits (aka bone density increase like nelie said) coming from using the platform as a support while doing strengthening moves (lunges, squats, pushups, etc).