Journalism as a Fourth Estate

The Fourth Estate is a societal or political force or institution whose influence is not consistently or officially recognized. "Fourth Estate" most commonly refers to the news media; especially print journalism or "the press". Thomas Carlyle attributed the origin of the term to Edmund Burke, who used it in a parliamentary debate in 1787 on the opening up of press reporting of the House of Commons of Great Britain. Earlier writers have applied the term to lawyers, to the British queens consort (acting as a free agent, independent of the king), and to the proletariat. The term makes implicit reference to the earlier division of the three  Estates of the Realm i.e. Government, Administration and Judiciary.

Why media and press are being called as '' fourth pillar '' or '' fourth estate?
The origins of the term “the fourth estate” are best explained within the context of the medieval “estates of the realm.” In medieval society, three “estates” were formally recognized: the clergy, the nobility, and the commoners. Each estate had a very distinct social role and a certain level of power, and the idea of the estates of the realm became so entrenched in European society that it still lives on, to some extent, although society is far more egalitarian today.

In the middle of the 19th century, people began referring to the press as a fourth estate, referencing the fact that most parliaments and other houses of government had an area set aside specifically for the use of the press, and pointing out that the press was a distinct group within the larger framework of the realm. Several historians credit the coinage of the term to Edmund Burke, who is said to have referenced the fourth estate when discussing the French Revolution, and Thomas Carlyle, a 19th century author, popularized the term.

The press plays a very important role in most societies, reporting on a wide variety of topics and creating powerful personalities who are relied upon for sources of information and commentary. Writing about the first estate in 1841, Thomas Carlyle pointed out that the press had a powerful role in parliamentary procedure, shaping the will of the people and influencing the outcome of votes among the government, as well. Carlyle also argued that the press was an important part of a democratic society, saying that writing gives people “a tongue which others will listen to.”

In Burke's 1787 coining he would have been making reference to the traditional three estates of Parliament: The Lords Spiritual, the Lords Temporal and the Commons. If, indeed, Burke did make the statement Carlyle attributes to him, the remark may have been in the back of Carlyle's mind when he wrote in his French Revolution (1837), "A Fourth Estate, of Able Editors, springs up; increases and multiplies, irrepressible, incalculable." In this context, the other three estates are those of the French States-General: the church, the nobility and the townsmen. 

Carlyle, however, may have mistaken his attribution: Thomas Macknight, writing in 1858, observes that Burke was merely a teller at the "illustrious nativity of the Fourth Estate". If Burke is excluded, other candidates for coining the term are Henry Brougham speaking in Parliament in 1823 or 1824 and Thomas Macaulay in an essay of 1828 reviewing Hallam's Constitutional History: "The gallery in which the reporters sit has become a fourth estate. The fourth estate refers to journalists and the business of journalism. 

Here is the classic explanation: “In May 1789, Louis XVI summoned to Versailles a full meeting of the 'Estates General'. The First Estate consisted of three hundred clergy. The Second Estate, three hundred nobles. The Third Estate, six hundred commoners. Some years later, after the French Revolution, Edmund Burke, looking up at the Press Gallery of the House of Commons, said, 'Yonder sits the Fourth Estate, and they are more important than them all "state of the realm."
So, the phrase is attributed to Edmund Burke (1729 - 1797), a British politician, as quoted in Thomas Carlyle's book, "Heros and Hero Worship in History" (1841): 
Burke said that there were three Estates in Parliament, but in the Reporters Gallery yonder, there sat a fourth Estate more important far than they all.
okay, now we will see the meaning to fourth estate: In a democratic set up there are three important pillars or estate you call them, first is legislature i.e. elected representatives, second is the executive i.e. cabinet of ministers that take decision policies of government, third is the judiciary that holds the rule of law and checks the law made by the govt are within ambit of the constitution and don't violate the fundamental law of the person. The press which does not have any constitutional or statutory powers but criticises the govt on wrong policies n make public opinion about policies that govt should have, so it is called the fourth estate.