Steem is a cryptocurrency! Which have its won blockchain! Like bitcoin. In future it can rise high to sky so if you have much money you can invest some in it. Also steem can be converted with other cryptos like btc,eth,ltc! Steem blockchain has an another coin named steem dollar (sbd). Currently sbd price is higher then steem. Mainly steem is a currency that is based on an blockchain.
The consensus mechanism is DPoS and it is 21 witness based. Steem is the token for rewarding the authors and curators in the steem community which is basically a social blogging community and based on the concept of proof-of-brain. Steemit is the first ever decentralized applications of the top of steem blockchain and it is the flagship dApp. Besides using the Steem blockchain for rewarding content and social interaction, projects like the trading card game Steem Monsters make use of the ability to store data using the JSON file format on the blockchain, making the proof of digital ownership possible for virtual goods