Who is Emmanuel Goldstein? And who is "Big Brother"?

Big Brother is the symbol of Oceania and the Party, Big Brother is Oceania's supreme leader, and is omnipresent through telescreen projections, coins, and even large posters warning, "BIG BROTHER IS WATCHING YOU." Big Brother is theoretically one of the original founders of the Party and the Revolution, but Winston assumes he does not exist, will never age, and will never die. He is the mouthpiece of the Party, and the symbol all Party members worship.

Emmanuel Goldstein is the enemy of the Party. We learn that he was a traitor who taught sin to the people. Like Big Brother, we are not sure if Goldstein is a real person.