It can be hard to understand a galaxy with the size and scale of that in which the Star Wars franchise takes place, but there are a few key parallels to be drawn with the real world. While it's often the least interesting aspect of the films, the Star Wars franchise is rife with fictional politics, and understanding the basics lends to a deeper understanding of the stories.
The eponymous wars that take place in the stars are fairly complex affairs, modeled originally after World War II and later after more modern conflicts. Those with the patience to pay attention will discover a ton of strategic detail, political intrigue, and real-world influence in the way Star Wars handles its galactic conflicts. Just like in the conflicts we know today, certain locations are of specific interest to one or both sides. In a galactic war, though, these are not cities or countries, but rather entire planets.
Muunilinst
This planet has not been depicted in the films, but it does serve as a setting for the classic Clone Wars animated series. The Battle of Muunilinst is a harrowing and hard-fought conflict in the early era of the franchise, in which a handful of specially trained clones fight off waves of droids.
The reason this planet needed to be so stringently defended is that it is the financial seat of power in the galaxy. This planet is essentially the Federal Reserve for the Star Wars universe. It holds most of the universe's currency, but it is also populated by its most important banks. Money is discussed extremely rarely in the Star Wars franchise, but all anyone would know about this planet after watching the source material would be that it's rich and important. Cash is evidently crucial to the ongoing war effort for both Separatist and Confederate forces, so Muunilinst is a key asset. The planet is known for playing both sides, making its whims important and dangerous.
Kamino
Fans will likely remember the importance of this waterlogged world. It houses the technology and facilities necessary for the mass cloning efforts that populate the Republic and Imperial army. The clone troopers are one of the most important military forces in the history of the franchise, both when they served the Republic and when they did the Empire's dirty work.
This planet was considered important enough to somehow hide from the archives, making it almost impossible to find. Cloning technology was so rare and crucial that even Jedi were prevented from seeking it out or learning anything about it. The planet that provides most, if not all, of the soldiers for the galaxy's armies is obviously going to be one of the most important places in the galaxy. Though fans haven't gotten to see much of it, Kamino is a key asset for any army.
Korriban
Also known as Moraband, this planet is less important for what it is now than it is for what it once was. The Star Wars universe has a few political concerns that the real world doesn't have, so there's no analog to what Korriban provides the galaxy. This planet is the original homeworld of the Sith, and the place where Dark Jedi intermixed with that species and forged the warriors of the Dark Side as fans now know them. The planet was declared abandoned shortly thereafter, but it also served as the site of the Sith Academy.
This is the home of evil throughout the galaxy, and while it can't exactly send delegates to the debate table, its history of evil is crucial to the history of Star Wars. Korriban is a desolate desert wasteland, but its ties to the Dark Lord of the Sith and the mysterious One Sith make it an eternal threat. Anything could be happening on a planet best known for being the site of most of the evil in the galaxy.
Alderaan
Though this planet is best known for being obliterated in the first few minutes of A New Hope, there was once much more going on behind its glossy towers. The adoptive home of Leia Organa turned out to be the perfect place for the daughter of Padme Amidala. As the galaxy fell to ruin and the Republic underwent the nightmarish fall into the Galactic Empire, Alderaan was ruled by Leia's parents. Senator Bail Organa remained in power as the Empire took over, and set to work creating the underground resistance that became the Rebellion.
The reason Darth Vader destroyed Alderaan wasn't just to demoralize Leia, it was to stamp out the primary home of resistance to his iron fist. Alderaan served as the home base of the Rebel Forces for the crucial early days, and that makes it a key player in galactic politics.
Coruscant
Imagine the entire galaxy had a single capital city and that city was the size of a planet. That's Coruscant. The political seat of power, the central trade hub, the Republic's headquarters, and much more lies in this central location, making it a point of tension in almost all conflicts in the galaxy.
In addition to that, the Jedi Temple is on Coruscant. Most of the important political events of the Star Wars timelines take place in this massive city, and that makes it the seat of power throughout the galaxy. During any of the franchise's wars, any factions involved will fight to control it.