Online social networks are communities of people who share common interests and activities. Social networking sites provide the ability to create a personal profile and various ways to interact with other people, such as  messaging, e-mail, video, text or voice chat, file sharing, blogging, and discussion groups. Social networking has revolutionized the way many people communicate and share information with each another. Social networking Web sites are used by millions of people everyday on a regular basis. For many people, online social networking has become a part of everyday life.

Most social networking services contain directories of categories (such as former classmates) and methods for connecting with people (usually based on some system of referral and trust).

Three very popular social networks:

MySpace has 120 million registered users who create their own profiles (Web pages) for the purpose of linking to friends, posting their interests, photos, music, and videos. MySpace is very popular in the United States and moderately popular worldwide. It is open to people 14 and older; most of the users are under 30. MySpace was purchased by News Corp. in 2005 for $580 million. It is now valued at over $65 billion.

Facebook has more than 80 million users worldwide. Users can join networks organized by city, workplace, school, and region to connect and interact with other people. People can add friends and send them messages and update their personal profile to notify friends about themselves. Recently, Facebook opened its platform to anyone to develop applications within Facebook. The site was initially limited to Harvard University students as a way to get to know other people on campus, but was later expanded to other colleges, and now is open to anyone aged 13 and over. Facebook was started in 2004 by Harvard student Mark Zuckerberg. Today,  at age 24, he is at the helm of this privately-owned company, turning down billion-dollar purchase offers. Facebook is valued at $15 billion.

LinkedIn is an on online social network that connects people with their friends, family, and business associates. It is primarily a business networking site that lets you post resume information and connect with other people in your profession. It currently has about 23 million registered users in 150 countries, with another 1.2 million signing up each month. LinkedIn started just 5 years ago, and is already valued at $1billion.

Sources: Wikipedia, USA Today, New York Post

There are also several social networks targeted at LDS audiences, such as LDS.net, LDS Online, and LDS Link Up.

Below is a short video that explains social networks: