Gatekeeping is one of the most prominent approaches of news selection. Originally, the approach focuses on the question what information is selected by journalists for public distribution via mass media and which factors are affecting this information selection. New and diverse forms of communication and large amounts of information on the internet have contributed to the fact that the audience and search engines play an increasing role in filtering information. This means that journalists are not the only gatekeepers anymore. The present volume introduces readers easy and comprehensible to theoretical perspectives, methodical approaches and empirical results of Gatekeeping from a communication science perspective. One emphasis will be current theoretical and methodical developments of this approach which have been caused by new and diverse forms of communication on the internet. The publication is intended to serve as a textbook for students, and also as a source of information for others interested people.