I promised to go into more detail on LinkedIn on May 14, and as you can tell, that hasn’t happened yet.

Until now. So here goes…

LinkedIn is the leading professional social networking site on the Internet. It has over 43 million members in more than 200 countries, and is home to active profiles for executives from every Fortune 500 company.

The site allows you to connect with colleagues and friends on a professional level, and provides an easy way to post your resume, contact information and other career-related items where potential employers can find them. It is the perfect solution for many people who find networking in person awkward, but are comfortable within the confines of social networking sites.

Among the 43 million members are ten million who have joined the website since the end of 2008.  Likely spurred by the recession and job fears, millions have turned to the networking site to build their personal network and maintain connections with colleagues and friends in a professional setting.

A sample profile page courtesy LinkedIn.

One of the best parts of the site is the “networking” part of social networking. Not only do you connect with people you know directly, but it shows who your contacts know as well, up to three levels of connections.

Say you’re looking to apply for a job at XYZ Corp., but you need someone to introduce you to boost your chances of a second interview. LinkedIn can help you discover that a former co-worker’s best friend works there and might be able to help you land the job.

Take my account as an example. I started it a few weeks ago because I realized I couldn’t write about something I had never used. In the course of maybe an hour of work spent finding connections, I currently have 40 contacts. But through the power of the network, I am connected to more than 2,200 people through friends, and over 246,000 people through their friends.

Though my LinkedIn network is limited by virtue of the number of people registered, and there are people I know professionally who are not on the site, I’m fairly certain I would not have quick access to about 245,950 of those contacts without LinkedIn.

Like me, you may be among the more than 200 million people with a Facebook account. So why do you need LinkedIn? For the same reason you do not count on MySpace for your professional web presence. Even Facebook is cluttered and chaotic, with photos, video, games, gifts, wall posts and tons of other junk that does not really project a professional image.

Still on the fence? Just know that nobody’s going to invite you to join Farmtown, send you a virtual strawberry-frosted cupcake gift or post a photo of you sucking down beers at the frathouse on LinkedIn.

Bottom line: Give it a shot. It’s free, and it could help you land your next job.