Ah, sorry I thought I answered your question... Witnesses job is like the miners in Bitcoin. That is, to use their computer to monitor the transactions and store the data on the blockchain... They are what keep STEEM blockchain running. They are rewarded by STEEM too, the amount is hidden for non-witnesses. Actually I think only the top witnesses get rewarded not sure about that.
With every update (called Hard Fork) to the the blockchain.. There are witnesses who agree to that update and those who disagree, the ones followed by the majority of community of STEEM are taken their decision granted.
So when you vote for a witness make sure he have the systems best interest in mind and not only what profits him, because if we voted to the wrong witnesses some of the future hard forks might destroy everything we care about.
EDIT: also your share is there now.