Most events in the Star Wars franchise have very little to do with the planet they take place on. The settings are excellent backdrops, but most feel more like Mario levels than fleshed-out worlds. There's the desert world, the ice world, the forest world, and so on. They have names, but only hardcore fans know the fine details. Some planets are central to the universe, but others are way out in the Outer Rim.
The governmental structure of the galaxy far far away changes multiple times in the Star Wars films. The Galactic Republic is supplanted by the Empire, which is replaced by the New Republic, which is slain by the First Order, which has been dissolved. Though the regime keeps changing, the seat of power remains the same. New rulers, same old throne.
What is the Outer Rim?
Despite the impressive technology of the Star Wars universe, the beings within have only mapped a percentage of the infinite expanse surrounding them. Beyond the bounds of the observable territories lies Wild Space and the Unknown Regions. The Unknown Regions have been identified on maps, but they've been largely unexplored. Wild Space is the infinite possible realms that exist beyond the edges of the maps. Right before entering the Unknown Regions lies the Outer Rim Territories. The Outer Rim Territories are the boundaries of well-explored space in the Star Wars universe, and that makes them the wild west of the wide-open stars.
The Outer Rim Territories are by far the largest sector of the observable universe. Explorers began charting the area thousands of years before the events of the Star Wars films. The process of mapping and taming the Outer Rim required immense expenditures of time, money, and technological innovation. Carefully regulated hyperspace lanes were constructed to allow swift travel between these new planets. Navigational beacons allowed newcomers to find their way through the newly mapped regions. The worlds within the Outer Rim are wildly varied, but many are rugged, dangerous, or openly hostile. Some have inhospitable environments like arid deserts or grotesque swamps. Others are home to aggressive predators famed for their lethal capabilities. Despite the unpleasant conditions of many Outer Rim Territories, their inherent draw was irresistible to many.
The Outer Rim Territories served as a sanctuary for individuals who viewed the governance of the Galactic Republic as repressive. Like any other frontier, pioneers came to the Outer Rim to find new lives. People experiencing poverty, discrimination, or governmental oppression could brave the challenging conditions of the Outer Rim. This sense of freedom also allowed criminals to flood the area. During the reign of the Galactic Empire, most Outer Rim planets became hives of scum and villainy. The Outer Rim was constantly under attack from pirates and slavers who were broadly safe from the power of law enforcement. This condition worsened under the heel of the Empire. Though the Imperial army made constant attempts to capture Outer Rim worlds, they found most of them unattainable. The Outer Rim remains a diverse chunk of the galaxy with many varied civilizations. Tatooine, Geonosis, Mandalore, Crait, and so many other key locations from the films are in the Outer Rim.
What are the Core Worlds?
If the Outer Rim Territories are the borders of the semi-civilized universe, the Core Worlds are its center. The Core Worlds are the seat of power in the galaxy. They possess the overwhelming majority of wealth, industry, and political influence. The most memorable Core World is Coruscant, a planet that is entirely covered by a single city. That city is the capital of the galactic government. It's home to the Senate and the primary Jedi Temple, as it has been for thousands of years. Every other Core World is secondary to Coruscant, but they maintain similar levels of financial success. Titans of industry like Corellia and Kuat are Core Worlds that create most of the galaxy's most popular space-faring vessels.
The Core Worlds are tame, civilized, and industrialized. Crime still exists in the Core Worlds, but it's rare and typically more white-collar. The benefits of the Core Worlds were numerous, but most were only available to the rich. These worlds gradually became overpopulated, forcing many denizens to escape to the next layer of the galaxy. Core World citizens moved from the Inner Rim, to the Mid Rim, to the Outer Rim to seek decent lives. Coruscant is the best example, but Princess Leia's late planet Alderaan was a founding Core World.
The Outer Rim Territories are wild and untamed. Those who choose to live there do so in desperation or desire for freedom. Most of the events of the Star Wars films take place in the Outer Rim Territories. When fans imagine themselves in the Star Wars universe, they should know that their experience will vary wildly based on which corner of the galaxy they happened to be born in.