The Estates-General was a general assembly representing the three classes or "estates" of French society: the clergy (the First Estate), the nobility (the Second Estate), and the peasantry (the Third Estate). The Estates-General was not a legislative body like the English Parliament; rather, its role was to advise the King, with whom all authority lay.*
* I have often imagined what it might be like to be a King.
I think my first rule would be to make all crime illegal.
Boom. Just like that. You're welcome.
It was infrequently called: before the onset of the Revolution, the last meeting of the Estates-General was in 1614. The Estates-General sat for several weeks in May and June 1789 to address the financial crisis facing the realm, thanks in no small part to the government's role in financing the American Revolution. The meeting quickly came to an impasse over the first item on the agenda, however: whether the Estates-General should vote collectively by estate (which would give an advantage to the first and second estates) or vote individually (which would give the more-numerous Third Estate the advantage). Deadlocked, the deputies of the Third Estate began to discuss political reforms rather than the financial crisis that had been the original agenda. The meeting of the Estates General dissolved when the Third Estate declared itself the National Assembly and announced that it would conduct the nation's affairs. The First and Second Estates were invited to join the Assembly, but it was clear which way the political wind was blowing. The French Revolution was beginning.