One key tenet of a liberal democracy, the dominant form of government today, is the separation of powers into the various independent branches of government, usually in the form of the legislature that makes the laws, a judiciary that interprets and applies the law and an executive that carries out the administration and operations of governing.
Societies in the past were relatively small and citizens were able to engage face-to-face or via handwritten messages in their deliberation and decision-making process. As populations grew larger participation in a democracy required mediation, i.e. communication is now mediated.
The earliest mass media was the newspaper, followed by the radio and television, and today, the Internet.
Because of its emerging function as a watchdog that monitors the running of the nation by exposing excesses and corruption, and holding those in power accountable, the media was regarded as the fourth estate, supplementing the three branches of government by providing checks and balances. The media also plays a more basic role as a provider of information necessary for rational debate.