LinkedIn is the largest online professional network active in over 200 countries and with 200 million members.
The website was launched for the first time in California, USA in May 2003. The managing director of LinkedIn is Jeff Weiner. The Executive Board consists of former executives from Yahoo, Google and Microsoft. The company's goal is to connect specialists and managers worldwide. According to Alexa, LinkedIn is one of the 500 most visited websites worldwide. 
LinkedIn offers its users access to people, posts, news, updates and insider information. The profile of the employee appears with a list of employment and education, which enables potential employers to make a well-founded selection of candidates for the position to be filled. In addition, the user can set up a link to their own website to actively promote their business.
The user can also register as a Premium Member via a paid account, which includes features such as the limitation of incoming messages, network statistics and a targeted search according to the job level, with costs varying between €20 and €350 depending on the service. One advantage of LinkedIn over competitors such as Xing is the fact that users can contact each other through the mediation of other members. This enables a serious network extension. Users can also rate other members. The profile then shows whether you are a motivated and committed employee or have the necessary competence for a senior position.
LinkedIn offers advertisers the possibility to place so-called "LinkedIn Ads". The advertisers can choose between CPC- or CPM-model accounting. The minimum CPC is 2 USD (as of December 2014).
An ad on LinkedIn looks like a text ad from Google AdWords, but has an additional image. A LinkedIn Ad consists of a maximum of 25 characters long header and a description with up to 75 characters. The company name can also be displayed. At the end of the text display, a link target is specified, to which the user reaches when he clicks on the corresponding display.
Requirement for the placement of LinkedIn Ads is a valid LinkedIn account.
LinkedIn Ads appear in all important areas of the network. Advertisements can be displayed on a member's profile page, as well as on the homepage, a user's inbox and search results page. It is also possible that the advertisements may appear on group pages.
There are a number of targeting possibilities for LinkedIn advertising. This means that advertisements can be placed according to business, sector, job title or target group's field of activity. Sociodemographic and geographical criteria such as age, region or gender can also be used. Interesting targeting options can also include "companies","career level" and "company size".
LinkedIn advertising offers companies an excellent opportunity to steer and promote recruiting, meaning that potential employees from selected companies can be specifically targeted for recruiting. The target group can also be tailored to a specific job you want to offer. In addition, this form of advertising could also be interesting for conventional advertising for insurance companies or financial service providers. The possibility of selecting the career level as a targeting option also indirectly captures the financial potential of the target group.
It would also be possible to advertise specifically on business accounts of companies to point out potentially better job opportunities in their own companies.
The manifold and very precise targeting possibilities are reflected in the high starting price of 2 USD per click. Depending on how many other companies advertise on LinkedIn, the click price could quickly become double-digit. 
On the part of the consumer protectionists, criticism of LinkedIn repeatedly arises. On the one hand, deleting a user account is extremely complicated, since the necessary functions are not obvious. Another point of criticism is the lack of data protection. In June 2012, a Russian hacker succeeded in releasing passwords of over 6.5 million members.
With the IPO in 2011 and the acquisition of SlideShare in May 2012, LinkedIn shows that the website pursues long-term economic goals. LinkedIn is a serious site for networking the working world. This is becoming increasingly important as globalization continues to advance.