LinkedIn is the largest professional business networking site covering over 200 countries. Founded in December 2002 and launched in May 2003. It is a business portal that connects everyone in the business field.
Source: http://www.linkedin.com/
Unlike facebook, twitter or myspace where you happen to bump into long lost friends or meet people haphazardly LinkedIn is specifically business oriented site where there are no such distractions. LinkedIn is not just great for making business contacts and contracts but also great for hiring people as per your requirement, one can even do reference checks through it.
It helps you to make your professional profile online; stay connected to your friends, family and colleagues and can get expert advice from professionals within the industry hence having more ideas and opportunities.
A mobile version of this site was introduced in February 2008 with limited features but still good enough to stay connected and do daily routine work.
LinkedIn with its 75 million users is way ahead of its major competitors Viadeo (30 million users) and XING (9 million users) in the market. Its membership is rapidly growing with the ratio of 1 new member per second. More than 50% of its users are from the Unites States and about 11 million are from Europe.
Signing up is free and simple and one can be up on it in no time posting profiles.
Source: https://www.linkedin.com/reg/join?trk=signin_join
LinkedIn allows two people, who link to each other, to exchange networks for professional goals. "Exchange networks" means that you will represent this person and their network to your network (on a case by case basis); and that you will represent your network to this person and their network. It's very "web of trust." Why professional? So that the point of the Interactions in this space are clear, and that everyone knows who to invite or not. (Would you introduce this person to your other trusted business contacts, at least for