Steem-blockchain requires a set of people to create blocks and uses a consensus mechanism called DPOS. The community elects 'witnesses' to act as the network's block producers and governance body. There're 20full-time witnesses, producing a block every 63-second round. A 21st-position is shared by the backup witnesses, who are scheduled proportionally to the amount of stake-weighted community approval they have.
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!)