What is social media?

Social media is best understood as a group of new kinds of online media which share most or all of the following characteristics:
Participation: social media encourages contributions and feedback from everyone who is interested. It blurs the line between the concept of media and audience.
Openness: most social media services are open to feedback and participation. They encourage voting, feedback, comments and sharing of information. There are rarely any barriers to accessing and making use of content – password protected content is frowned on.
Conversation: whereas traditional media is about “broadcast”, content transmitted or distributed to an audience, social media is better seen as conversational, twoway.
Community: social media allows communities to form quickly and communicate effectively around common interests – be that a love of photography, a political issue or a favourite TV show.
Connectedness: Most kinds of social media thrive on their connectedness, via links and combining different kinds of media in one place.

Basic types of social media
At this time, I think that there are basically six kinds of social media. Note though that innovation and change are rife in social media.
The most common kinds of social media are blogs, social networks, content communities (sometimes called folksonomies), wikis, podcasts and forums. You may have heard of many of these, and we’ll go into a little more depth on these later, but here are some one line descriptions to be going on with:
Blogs: perhaps the best known form of social media, blogs are online journals, with entries appearing with the most recent first.
Social networks: these websites allow people to build personal websites and then connect with friends to share content and communication. The best known example of a
social network is MySpace, which has over 107 million members.
Content communities: communities which organise and share particular kinds of content. The most popular kinds of content communities tend to be around photos (Flickr),bookmarked links (del.icio.us) and videos (YouTube).
Wikis: these websites allow people to add content to or edit the information on them, acting as a communal document or database. The best-known wiki is the online encyclopaedia which has over 1.5 million articles published in English alone.
Podcasts: audio and video files that are available by subscription through services like Apple iTunes.
Forums: areas for online discussion, often around specific topics and interests. Forums predate the advent of the term ‘social media’ and are a powerful and popular element of online communities.
資料來源: http://www.spannerworks.com/what-we-think/our-research/