Steem is an open-source, public, blockchain protocol powered by the native cryptocurrency STEEM. The protocol is designed to operate as a decentralized content management platform with 3-second confirmation and fee-less transactions. Once stored on the blockchain, the content becomes publicly available for developers to create apps and websites. The blockchain was launched in March 24, 2016 and the first token rewards were distributed on July 4th 2016.
Steem, contrary to most blockchains, is application specific. It focuses on being a very efficient way of storing content in a decentralized manner and then autonomously distribute tokens to the authors of that content based on crowdsourced stake-weighted voting.