Hi everyone,
So, you haven't seen Star Wars: The Force Awakens yet? Good... That Galaxy far far away is a pretty big place, and a lot has happened since we last visited it in Star Wars Episode VI: Return of the Jedi.
There are spoilers in here, but they come later and regard Princess Leia and the Resistance only, I will warn you before that happens.
The Battle of Endor saw a decisive victory for the Alliance to Restore the Republic, with the destruction of the Second Death Star and the death of Emperor Palpatine and Darth Vader.
The Alliance reformed into the New Republic and sent messages to planets, encouraging them to rebel against the Imperial Garrisons on their planets. However, not every planet did so and the Empire held on to some of them. This led to the Civil War.
If you remember in the trailer the desert planet, Jakku, not Tatooine, that is where the final battle of the Civil War between the now massively expanded New Republic, thus the Star Destroyers littering the desert.
After this the Empire retreated to the unknown territory planets, and eventually signed a disarmament treaty with the New Republic. The Republic [and supposedly the Empire] then began to retire their large fleets, leading to the position we come to in the movie.
Meanwhile, the New Republic had to prove it was different from the Galactic Republic that the Empire replaced. The first way it did this was not to move the Senate back to the old building (seen in the prequels) on Coruscant (as far as I know it stayed part of the Empire, but I could be wrong).
Instead, the Senate of the New Republic moves to different host countries, also the Chancellor is no longer called the Supreme Chancellor (too Imperialistic, I guess). At the time of the Force Awakens the Chancellor is a guy called Lanever Villecham and the Senate presently sits on a planet called Hosnian Prime.
Ok, so spoilers (potentially, not really) will be below so stop reading and come back afterwards if you would prefer.
General Leia is not part of the Republic Senate in the Force Awakens. This is because she was suspicious of the Empire and believed, unlike the Republic, that they wouldn't disarm. This is why the Resistance force is so small in the movie, like ten X-Wings. It actually isn't sanctioned, fully, by the Republic. Leia actually has become annoyed with how slow the Republic Senate is to make decisions, just like her mother was when she voted no confidence in the Supreme Chancellor of her day!
The Senate began to see Leia as irrational and stuck in the past, thinking there would be war when the New Republic attempted to tell everyone there would be peace. Leia and the Senate eventually parted ways, though she still has a representative there. She then contacted the retired Admiral Ackbar, who first fought for the Republic in the Clone Wars, then for the Alliance and was drawn out of retirement to lend his military knowledge to the Resistance.
