In simple terms:

Social media is formed mainly by the public as a group, in a social way, rather than media produced by journalists, editors and media conglomerates.

Further, as Wikipedia (itself one of the best social media example!) elaborates:

Social media is media designed to be disseminated through social interaction, created using highly accessible and scalable publishing techniques. Social media uses Internet and web-based technologies to transform broadcast media monologues (one to many) into social media dialogues (many to many). It supports the democratization of knowledge and information, transforming people from content consumers into content producers.

Social media is different from Mass media. That’s where technology came into the picture and internet saw a new paradigm in form of Web 2.0 technologies. Businesses also refer to social media as consumer-generated media (CGM) and every effort being taken by smart managers of today’s fast paced economy to garner mutual benefit out of it.

Websites like, Facebook, Orkut, Wikipedia and LinkedIn are leading examples of Social media revolution. The democratization of information can also be felt from a blog wave that has swept the intellectual class and a lot of us are voicing our opinions and issues online these days. So from Information Age we are seeing a gradual shift towards Attention Age.