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The Steem platform is secured and supported by a network of witnesses all around the globe, ie, database and operations aren't centralised in companies like reddit inc / facebook inc. Witnesses are the ones with the computing resources to upkeep the network. Anyone can propose themselves to become a witness. Whether or not they become one will be through witness voting.

Thank you. I was getting confused on what a witness is and what they do. Now I know

No problem :)

thanks kevinwong