The best way to define social media is to break it down. Media is an instrument of communication, like a newspaper or television advertisement, social media would then be through the use of a social medium to promote communication. In online terms, social media would generally be a website or application that not only offers you information but interacts with you. This interaction could be as simple as requesting a comment or a vote on an article, or can be as complex making recommendations to you based on previous interaction or popularity based on other users with similar interests.
Think of regular media as a one-way street where you can read a newspaper or listen to a report on television, but you have very limited ability to give your thoughts on the matter.
Social media has been around since humans began to interact with each other. Some of the earliest examples of human social media are cave wall paintings. While humankind has evolved beyond drawing on cave walls, for the most part, social media today is very similar in many ways to cave paintings with people posting images or text onto space online, amusingly referred to as walls to this day.
Social media today differs from traditional media in many ways including:
Quality - Traditionally media may have been published to reach a specific audience within a defined niche. Social media may result in a high variance in distribution from very high-quality to low-quality audience.
Reach - While both traditional and social media channels can reach a substantial audience, typical media tends to be more organised in production and dissemination, whereas social media are by their very nature more decentralized, less hierarchical.
Frequency - The time of both advertising and information display is longer in social media channels than in traditional media.
Accessibility - Production of typical media tends to be quite costly; social media tools are generally available to the general public at little to no cost.
Usability - Traditional media production typically requires specialized skills and training. Conversely, most social media production requires only modest reinterpretation of existing skills; in theory, anyone with access can operate the means of social media production
Immediacy - Traditional media, once produced may result in long delays in response time. Social media can result in virtually instantaneous responses.
Permanence - Once created, traditional media can't be altered (once printed, published and distributed changes can't be made to the same creative). Social media allows for almost instant alterations through comments or editing.
Top Social Media Channels (as per number of registered users):
More comprehensive list: http://en.wikipedia.org/wiki/List_of_social_networking_websites
The amount of internet users who spend more time on social media channels, as such social media is becoming an ever more important channel for news and information distribution and consumption; in many cases taking over the functions of traditional media. Don’t let your competitors beat you out in the socialsphere. Your next prospect could possibly come from a social media channel.