system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Some questions about the Empire.

1) What is a Moff?

2) Where do Moffs, Admirals, Senators, and generals list in the Imperial hierarchy status?

3) Did anyone in the Senate openly oppose Palpatine's change to the system from a Republic to an Empire?
gpt
1) a Moff is the governor of a sector of the Republic/Empire. In the old days, a Moff governed one of a thousand sectors of the galaxy. The position waned in later years, but Chancellor Palpatine reinstated it during the Clone Wars. 

2) The Moffs are territorial governors, where Senators represent a planet or sector. (breaking the 4th wall) A Moff can be thought of as the governor of a state, where the Senator can be thought of as a federal representative. Admirals are in charge of military assets.

3) It is known that Alderaan, Corellia, and Chandrila were among the first planets to secede from the Empire when the Corellian Treaty was signed. Though this was orchestrated by Darth Vader as an attempt to capture and stamp out the sparks of rebellion, instead it led to several other planets forming resistance movements against the Empire, including Sullust, Dantooine, Duro, Kashyyyk, and others. Approximately 2 years after the Corellian Treaty was signed, Emperor Palpatine dissolved the Imperial Senate as an "emergency measure" due to widespread dissemination of the Declaration of Rebellion. 

Following the dissolution of the Senate, the Emperor was able to instruct the regional Moffs and Grand Moffs directly without the bureaucracy of the Senate interfering.