A video produced by Common Craft (link at the end of this post)uses the story of a fictional town called Scoopville to explain social media in a way anyone can understand.
Scoopville, is a town famous for ice cream. For a long time, the ice cream market was dominated by one large company offering only the three basic flavors: chocolate, vanilla and strawberry. But then one day, inexpensive ice cream makers appeared in Scoopville, and the local population had the opportunity to experience new flavours. In time people began to see ice cream in a different way. It no longer came from a factory but also from firends and neighbours. Visitors poured into Scoopville, but became overwhelmed by the choices available. So a resident set up a bulletin board in front of his house that enabled visitors to describe his ice cream, rate it and leave messages for others. The feedback enabled residents to improve and market their ice cream, and helped potential customers find exactly what they wanted.
A summery story to enable you to learn more about social media.