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The steemit platform has three tokens: Steem(the cryptocurrency of steem blockchain),Steem based dollars(SBD) which are tokens worth approximately 1 USD and the last one is STEEMPOWER(SP). Steem power is the influence token on the steemit platform slightly relatable to reddit's karma. SP measures your influence of your upvotes on the platform, more you have it more the value of your upvote. It also influences your reward share in similar fashion. The value of SP is the same as Steem(cryptocurrency).

Hope it helps. Thanks!

Steem is a blockchain-based award platform for publishers to monetize content and develop communities.

About USD Prizes paid since June 2016:

$ 22,728,958

What is a Smart Media Token?
Smart Media Tokens (SMT) are original digital assets blocked by Steem that can be launched quickly by anyone to help monetize online content and create incentives to encourage desired user behavior.

They are like ERC-20 Ethereum tokens, but with a built-in 'Proof-of-Brain' feature and a token distribution reward system designed specifically for digital content businesses.

Community incentives
'Brain Proof'

Proof-of-Brain is a kind of reward token algorithm that encourages people to create and manage content.

This allows tokens to be distributed by "upvote" and "like" algorithms, and can be integrated with websites to align incentives between application owners and community members to spur growth.