Jesus, everybody keeps asking this question.
Synereo is like Facebook/Twitter
Steemit is like Reddit
DECENT is like Netflix/Youtube
The first two are social networks. Synereo gives you a personal wall, while Steemit has a shared front page for everybody. DECENT is not really a social network, but more about non-social multimedia. The original creator is tracked, and content such as books, songs and movies are disseminated without the use of a middleman
Thank you
Just to add, DECENT is focused on its long-term goals that have been specified in our roadmap. It's not meant to become another blockchain app rather a network of connected individual and organizations that will build the infrastructure of decentralized content distribution network. As mentioned above, DECENT is not a social network even though it has some social aspects e.g. reputation