Vests are the secret currency in Steem. They represent the size of your stake in Steem, or your SteemPower. The front end interface hides this, and shows you SteemPower instead of vests.
Whenever you power up Steem, you are really converting to Vests, and powering down is changing your Vests for Steem again.
ThanK YOU .. clear - ))
.. i appreciate this - )