Steemit is a social media platform that links cryptocurrency to user contribution, so imagine if you were able to earn some cryptocurrency every time someone ‘likes’ your post or share it with other users when you are on facebook. The Steem blockchain (like the Bitcoin or Ethereum blockchain) allows applications to be build on top of it to provide the same type of system for video content (www.dlive.io), audio (DSound - Decentralized Sound Platform), photos (Steepshot) and the list goes on.
What is important to know is that like any cryptocurrency the value can fluctuate, and like most social media platforms there are also people who will act in a malicious way that damages the reputation of the brand.
As a current user I find that the platform is an excellent way to learn about all things relating to cryptocurrency. There are many people there who provide excellent information and insights about the future digital economy and plenty of activities that stem from the social media platform in different groups and projects not just primarily based in the US but all around the world.
The short answer is that Steemit is a legitimate social media platform that you can earn cryptocurrency by contributing content, but that there are also scammers that either manipulate the system or trick other people into handing over their money.