The galaxy consists of a number of worlds, most of which are initially unowned by any player. The precise number of worlds varies per game (and is loosely based on the number of players); in any particular game, there may be dozens of worlds, or there may be hundreds.

Most worlds are connected to two, three, or four other worlds. Some worlds might have only one connection; some may have as many as five or six. Ultimately, all worlds are interconnected in a single contiguous Web.

In RSW Core, unlike in some other RSW variants, all worlds are the same. Every world that you own is worth 20 points to you each turn that you own it, and every world will produce ships each turn that you own it.

The ships that accumulate on a world will remain in defense of the world itself (they're called "defensive ships" or "D-Ships" for short), until you transfer some or all of them onto an orbiting fleet. It is also possible to fire D-Ships directly at an enemy fleet at the same world--see combat for more.

As you visit new, unowned worlds in the galaxy, you will automatically plant your flag on them, so to speak, and claim them as your own. The exact rules of ownership are a little more complex, but in general, you will own any world that you are the first to visit.