Delegation is simple. It is a "loan" of Steem power. New users are given a loan, from the platform, to help them get started. Once you've gotten past a certain point, that Steem will be removed from your account. Until then, it is your voting power to use how you want. You cannot sell it, or power it down.

Witnesses are members that agree to run a computer that holds a "node" or part of the Steem block chain, to help keep track of transactions on the blockchain. They are paid for their service, and they vote on some issues regarding changes to the platform.

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