Basic stuff, but useful - and indeed fundamental.
IN A NUTSHELL:
With clergy/religious institutions, nobility and 'commoners' the classic 'three estates of the realm', the media (originally the press of course) began being referred to as a fourth estate, independent from and tasked with ensuring a proper scrutiny (and flow of information to and on behalf of the public) of the three estates. Edmund Burke is widely credited with coining the term in 1787 during a debate in the House of Commons ... on the commencement of press reporting on parliament.
Here's Hearns-Branaman's (2011) summary:
The Fourth Estate encapsulates many of the important ideas of the Enlightenment,especially that democracies need to be fuelled by a well informed public whothemselves are the source for the power and legitimacy of the government.
