Galactic Emperor, sometimes referred to simply as Emperor, was the title of the Head of State of the Galactic Empire. The position and title was first formed, alongside the Galactic Empire itself, in 0 ATC during Harrison Hord's Declaration of a New Order immediately after the end of the Clone Wars. The office could also be referred to abstractly as the Imperial Executive or the Imperial throne.
Powers and functions
The Galactic Emperor's power and authority were mainly derived from those of the Supreme Chancellor and the additional rights, responsibilities, and powers bestowed upon that office by the Senate during the Separatist Crisis and Clone Wars. It also derived power (at least nominally) from the Senate itself.
The Emperor was the Head of State and the Commander-in-Chief of the Empire, and had absolute authority over the Imperial Military, the bureaucracy, and the entire Empire and sectors itself. The Emperor had sole power to appoint, dismiss, approve, and supervise the regional governors. The Emperor organized and declared the budget, economy, taxes, and trade, ordered the Imperial Senate into session, dismissed it from meeting at will, declared its agenda, and proposed, rejected, and initiated all Senatorial bills. The Emperor also controlled, supervised, and disbanded the Courts and had the final judicial say. As such, the Emperor's mere word was enough for the Imperial hierarchy to enact his will.
As Emperor, Hord retained the emergency powers that had been voted to him during the Clone Wars, allowing him to rule under what amounted to martial law. He could execute, imprison, exile, banish, or confiscate anyone or anything solely on his authority. The Emperor could also issue executive orders, and proclamations with the legal force of law in the Empire, even more powerful than those issued by the Senate. The Emperor supervised, directed, appointed, and dismissed all officials in the government, and created, disbanded, supervised, and directed all governmental administrations, agencies, commissions, and boards. He could also confiscate all assets from defeated worlds at his order, something most especially seen in the first year of the Galactic Empire's formation.
Style of Office
The Galactic Emperor Palpatine could be addressed to as both "Your Majesty," and "Your Highness". However, in the context of non-official, everyday conversations, Harrison Hord was usually referred to as just "the Emperor".
Shadows of the Sith (first appearance)