Blogs

A Blog is a web site used for personal discussions or as an informational site for other people to read.  The term "Blog" was coined as being short for "Web Log".  There have been many social blog sites created that help people develop and maintain their personal blog as well as discover and connect to other blogs that may be interesting to them.  Sites such as Tumblr, Blogger, Wordpress, and even Facebook to name a few.  Blogs are a great tool for communicating and sharing interests and for finding other people who have the same interests.  Some blog sites have become major social networks for people to find and create new social circles based on particular interests.  Users on these sites can comment and share their thoughts with the original poster or even 'reblog', meaning to share the original content with their own followers.
Creating blogs can be helpful to a persons career as well.  Many companies that are hiring technical people like to see a potential candidate has a technical blog.  This shows that the candidate has a personal interest in what they are talking about that extends outside of just their job functions.  It shows an interest in growing and learning new things, as well as participation in a technical community.  Blogs are a great way to showcase personal projects and to get others interested in the work you are doing.
The Nielsen Company estimates that, as of 2011, there are over 156 million blogs in existence and that number is continuously rising.  This shows that Blogs as a platform has an incredible potential to reach millions of people.

References:
The Neilsen Company- Millions More Bloggers. http://www.nielsen.com/us/en/newswire/2012/buzz-in-the-blogosphere-millions-more-bloggers-and-blog-readers.html