In England, the Estates of the Realm are the Clergy, the Lords and the Commons. What is known as the "Fourth Estate"?

Answer 1

The press
The earliest use of the term is Thomas Carlyle's book "On Heroes and Hero Worship" (1841): “[British politician Edmund] Burke said there were Three Estates in Parliament; but, in the Reporters' Gallery yonder, there sat a Fourth Estate more important far than they all."