Social Media in Plain English

My definition:

Social media = shared media

Social media is:
-  a set of technologies, tools and platforms facilitating the discovery, participation and sharing of content
-  content created by people using highly accessible and scalable publishing technologies
-  the transformation of monologues (one to many) into dialogues (many to many)
-  NOT a channel or a place to broadcast – it is a conversation network.

In video (by CommonCraft)

Social Media Optimization – Leverage Your Business With Social Media