What are the most popular social media sites?

Nowadays, everybody resorts to using Facebook, Twitter, LinkedIn, WordPress, and Blogger.

Facebook: Facebook is a social networking service launched in February 2004, owned and operated by Facebook, Inc. As of September 2012, Facebook has over one billion active users, more than half of them using Facebook on a mobile device. Users must register before using the site, after which they may create a personal profile, add other users as friends, and exchange messages, including automatic notifications when they update their profile. Additionally, users may join common-interest user groups, organized by workplace, school or college, or other characteristics, and categorize their friends into lists such as “People From Work” or “Close Friends”.
You can look into Facebook here: www.facebook.com

Twitter: Twitter is a real-time information network that connects you to the latest stories, ideas, opinions and news about what you find interesting. Simply find the accounts you find most compelling and follow the conversations.
At the heart of Twitter are small bursts of information called Tweets. Each Tweet is 140 characters long, but don’t let the small size fool you—you can discover a lot in a little space. You can see photos, videos and conversations directly in Tweets to get the whole story at a glance, and all in one place.
You can look into Twitter here: www.twitter.com

LinkedIn: LinkedIn operates the world’s largest professional network on the Internet in over 200 countries and territories. Its mission is to connect the world’s professionals to make them more productive and successful. The company is publicly held and has a diversified business model with revenues coming from hiring solutions, marketing solutions and premium subscriptions.
You can look into LinkedIn here: www.linkedin.com

WordPress: WordPress started as just a blogging system, but has evolved to be used as full content management system and so much more through the thousands of plugins, widgets, and themes, WordPress is limited only by your imagination. (And tech chops.) Open source WordPress has been incredibly successful and risen from a handful of users to the most-used blog tool in its category. However, as easy-to-use as we could make the open source package, there was still a barrier in that it requires a hosting account, a database, FTP, and a whole alphabet soup of acronyms that make normal people like you and me dizzy.
You can look into WordPress here: http://en.wordpress.com/about/

Blogger: We created Blogger to give you an easy way to share your thoughts — about current events, what’s going on in your life, or anything else you’d care to discuss — with the world. We’ve developed a host of features to make blogging as simple and effective as possible.
You can look into Blogger here: www.blogger.com