They say timing is everything in life, and that this toy makes your timing better. There are four modes:  try to stop the timer as close to five seconds as possible,  try to stop it as close as possible to 10 seconds, but without going over! (Price is Right, style)  practice mode  challenge mode.
This is an awesome and unique way to, quite literally, waste time. Click this link to see an hilarious video from the manufacturer.