Galactic Civilization
History
The history of galactic civilization goes back at least 36,000 years. For most of that time, civilization was governed by the Republic, a representational democracy which lasted, in one form or another, for over 25,000 years. The highest power for order in the Republic were the Jedi Knights, a group of monastic mystic warriors who used a magic like energy called the Force to gain superhuman powers. The Star Wars films cover the "modern" or "current" period. The Republic has been overthrown by the election of an evil, dark jedi who instituted an empire (there are a lot of parallels to Nazi Germany). The fall of the Republic and beginning of the Empire is shown in the prequel trilogy. The original trilogy covers the Rebellion against the Empire showing the high points in a civil war to overthrow the evil Emperor and return to democratic rule, forming the New Republic. The original republic then becomes known as the "Old Republic".
However, restoring the legitimate government was not easy nor fast. Seizing the galactic capital took more battles and 2.5 years after fall of the Emperor. Remnants of the Empire continued to fight and resist for years, even decades, in a way becoming their own rebellion against the New Republic. However, former imperial forces continued to refer to their enemies as "Rebels", implying they themselves were the rightful government. In most cases, this was simple propaganda from self-serving warlords, but some did want to restore the Empire (although most imagined themselves on the throne, as the Emperor was dead).
Population and Astrography
Civilized territory ruled by the Old Republic/Empire/The New Republic covered two thirds of the galaxy. There were many intelligent species, humans being the most prevalent. Under the Republics, humans were a member species, but not rulers. The Empire, on the other hand was, at least as depicted in most sources, ruled by humans. The Imperial government and military seemed to be entirely human and racist, regarding non-human species as inferior.
Different sources state different numbers of inhabited worlds, from as ridiculously high as 1.5 million member worlds and 69 million colonies to a much more reasonable number of over 24,000 worlds. I'm going with 24,000. There are known home worlds for many species, but humans are such an old species that their home world is believed to be the capital world, Coruscant, but even that may be conjecture. There are famous human dominated worlds like Corellia, Chandrilla, and Alderaan but there are so many inhabited worlds that you can make up your own home world for your characters, and we'll just drop it in on the map. Most worlds have a mix of species that have settled there. Tatooine for example has humans, Rodians, Twi'leks, and two native (possibly related) races, Jawas and Sand People. The spaceport cities have other aliens as well, but they may not have significant communities. However, from what little we have seen, the non-human home worlds are dominated by the native race with small amounts of other races.
Interstellar travel is by the hyperdrive, a faster than light system that moves ships into an alternate dimension with different laws of physics, allowing ships to travel at incredible speeds. Even a slow standard hyperdrive moves a ship at over 1,000 light years per hour. Nearby systems can be reached in hours and ships can travel well plotted routes literally across the entire galaxy in days (Star Wars has one of the fastest travel systems in science fiction). Ships cannot enter or leave hyperspace too close to a large body, such as a planet or star (recent movies have played fast and loose with this). While the ships have sensors to prevent them from getting too close by forcing them to drop out of hyperspace, it is possible to hit the danger zone around a massive star or black hole too quickly for the safety system to work and the ship can be destroyed or forced out of hyperspace with damage.
Technology is fairly uniform across the galaxy. While some worlds may have better technology and infrastructure, even poor worlds like Tatooine have anti-gravity speeders and droids. They might not be able to build them and maintenance may be poor, but they can be imported.
There are dozens if not hundreds of intelligent species in the galaxy. See Star Wars Playable Races for a selection for player characters. Droids could be considered a race as well, as most are intelligent enough to be self-aware and qualify for sentience. However, even in the Republic, droids are property, which honestly makes them slaves. In the books, some droids do earn their freedom and the term is the same as used for freeing slaves in real history. But they completely gloss over that in the movies. Some people regard their droids like beloved pets, but most treat them as tools.
Technology
As mentioned, star travel is by hyperdrive and sentient droids are everywhere. Artificial gravity is universal in ships. Primary weapons are lasers (usually used as heavy weapons on tanks, fighters, and ships) and blasters which trade range for more destructiveness and tend to be used as hand weapons. Interstellar communication is possible, and seems to be almost instantaneous, but the bandwidth is very narrow. You can't transmit any worthwhile amount of data, which is why Leia was hand carrying the Death Star plans. Even voice communication can be spotty, and live video is only possible with the best equipment (bases and large ships) and at relatively short ranges. There are advanced bionics and prosthetics, but they often have mental adaptation issues (cyberpsychosis!) and are generally shunned. The center of medical treatment is a substance called bacta, which induces near miraculous healing and regeneration. It can be applied topically; seriously wounded patients are often submerged into a tank with breathing apparatus. It could not regenerate severed limbs, but even deep wounds could be healed almost completely.
