Witnesses makes our post appear on steem blockchain, for people to see. The communuty elects witnesses to act as the network's block producers and governance body. In excess, if there are no witnesses, there will be no steem.
These are the witnesses i voted for
RE: Show Us Your Witnesses Weekly Contest: A Concept To Drive Up Witness Voting Engagement Among Steemians (Episode #4 Result Update; Episode #5 — 6SBD Prize Pool; 3 Possible Winners!)