A friend asked me for a brief overview of Steem, my reply was the following.
Steem is Social Networking with Rewards
Steem is an aggregate social networking site where users, or "Steemians", post original content, links from the Internet and questions. Steem users upvote or downvote this content to promote interesting post and reward the author. As a post's popularity increases, it gains more visibility and the author is likely to receive even more rewards for their effort.
Posts that are downvoted or fail to garner many upvotes quickly vanish from view as higher quality content rises to the top of the "Hot" and "Active" list on the Steemit front page. Steem users receive rewards for upvotes on their original content, links and comments, but they can also lose rewards for unpopular post by being downvoted, especially by large stakeholders in the Steem platform called "whales" -- giving an incentive not to just post, but to post high-quality or especially interesting and relevant content. Any Steemian can comment on posts, and their comments can generate interesting debate or give further details on the topic at hand.
Steem Curation and Moderation
In addition, anyone can read content posted on Steem without an account, and users can be entirely anonymous if they choose. Steem governs its users behavior through Community moderation, Steemetiquette if you will. There are no set guidelines as of yet, like on Reddit, but they are being created organically and are self enforced by the Community through their combined voting power called Steem Power. These guiding principles in many ways encourage quality original content from fellow Steemians, otherwise the user is simply wasting their time since they will likely not earn any rewards for posting low quality, undesirable content or spam.
Voters on Steem are called "curators" and are encouraged to evaluate content, sources and links to find high quality information, then vote and moderate based on on the information's factuality, relevance and quality, rather than on opinions. Giving credit where it's due and citing sources is encouraged, since the original poster is being rewarded for the content, original content is preferred when it comes to handing out rewards.
Steemetiquette
Using proper Markdown syntax, spelling and grammar is also rewarded as it breeds intelligent discourse. Steemians are seen as more reliable and more respected if they can write well thought out original content. Users who simply link to others work or do not take the time to create a post which is easy to read or appeasing to the eye are rarely rewarded for their effort, making it worth the minimal extra time to format their content properly and proofread prior to posting.
At times incorrect information or low quality post do rise to the top via the crowd-sourced voting mechanisms, any post that has gained enough popularity will eventually be scrutinized by Steemetiquette, trolls and top curators. For this reason, this presents a problem for anyone looking to use Steem as a marketing platform. Although there is no such thing as a "ban" on Steem, users who continually abuse the platform by posting low quality content, marketing material or spam will be called out on it and downvoted so the post is hard to locate.
I encourage you to explore Steemit.com and the Community for yourself. Steem has something for everyone and rewards those who help contribute to the Community in a positive way, be it via original content or quality curation of others content, which helps maintain an enjoyable experience for all Steemians!