Social networks are the relationships that tie us together. Think about what happens when you meet someone new. You ask where they work, where they grew up, where they went to school. Eventually, you realize that your childhood friend was in this guy's fraternity in college. Even though you've never met before, you're both part of the same social network -- a friend of a friend.

social network
© iStockPhoto/Franz Pfluegl
Social networks allow friends to connect.
The term "social network" has been around since the 1950s, but the meteoric rise of social-networking Web sites like MySpace, Facebook and Linkedin has turned a dusty sociological phrase into the hottest buzzword of the Internet age.

A social network is a social structure that maps out the relationships between individuals. Technically we all belong to one giant social network, but we also belong to smaller, tighter social networks defined by our families, our friends, where we live, where we work, where we went to school, our hobbies and interests and much more.

Social Networks History
In the early 1930s, a self-published psychologist named Dr. Jacob Levi Moreno introduced the sociogram, the first formal attempt to map out the relationships within a group of people. Moreno's sociogram -- a cluster of individual points, or "nodes," connected by straight lines -- became a powerful tool for identifying social leaders, outsiders, and what he called the "sociometric star," the person to whom all others are connected [source: Psybernet].

In 1954, anthropologist J. A. Barnes used the phrase "social network" to describe the complex relationships in a Norwegian fishing village [source: The Bumble Bee].

If you sat down with a pen and paper, it would be difficult to map out all the people with whom you're connected and all the people with whom they're connected. That's why social-networking Web sites are so powerful.

Social-networking sites "make invisible social networks visible" by allowing us to see (with pictures and links) who our friends are, who our friends' friends are, and who our friends' friends' friends are -- all in an easy-to-use interface [source: Wireless Jobs.com].

When you create a profile on a social-networking site, you literally put yourself on the social-networking map. You can use the Web site to:

  • look up old friends; make new ones
  • share music, photos and videos
  • join groups based on interests such as politics, hobbies or favorite TV shows
  • find jobs or love; or browse for the weirdest profile picture

How popular are social-networking sites? According to ComScore, MySpace drew more than 114 million visitors ages 15 and older in June 2007, a 72 percent increase over June 2006. Facebook jumped 270 percent in the same year, up to 52 million visitors a month. According to Alexa, seven of the top 20 most visited Web sites in the world are social-networking sites, such as MySpace or Friendster, or contain significant social-networking components like YouTube or Hi5.

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­But as social-networking sites go mainstream, the demographics are shifting. By August 2006, more than two-thirds of MySpace visitors were over 25 years old, with more than 40 percent between the ages of 35 and 54. Now that non-university students can sign up for Facebook accounts, more than half of that site's members are out of college. [source: ComScore]

This isn't just a U.S. phenomenon. Social-networking sites have gone global. In June 2007, Google's Orkut drew 49 percent of its visitors from Latin America (mostly Brazil) and 43 percent from the Asia-Pacific region. In that same month, a full 89 percent of visitors to Friendster were from the Asia-Pacific region and 63 percent of visitors to Bebo were from Europe [source: ComScore].

In this HowStuffWorks article, we're going to explain how social networks work, how technology aids in forming and maintaining social networks, and how Web sites take social networks to the next level and beyond.