The Culture, living mostly on massive spaceships and in artificial habitats, and also feeling no need for conquest in the typical sense of the word, possesses no borders. Its sphere of influence is better defined by the (current) concentration of Culture ships and habitats as well as the measure of effect its example and its interventions have already had on the 'local' population of any galactic sector. As the Culture is also a very graduated and constantly if slowly changing society, their societal boundaries are also constantly in flux (though they tend to be continually expanding during the novels), peacefully 'absorbing' societies and individuals.

While the Culture is one of the most advanced and most powerful of all galactic civilizations, it is but one of the "high-level Involved" (called "Optimae" by some less advanced civilizations), the most powerful non-sublimed civilizations which mentor or control the others.

An Involved society is a highly advanced group that has achieved galaxy-wide involvement with other cultures or societies. There are a few dozen Involved societies, and hundreds or thousands of well-developed (interstellar) but insufficiently influential societies or cultures, or those well-developed societies known as "galactically mature" which do not take such a dynamic role in the galaxy as a whole. In the novels, the Culture might be considered the premier Involved society, or at least, the most dynamic and energetic, especially given that the Culture itself is a growing multicultural fusion of Involved societies. The Involved are contrasted with the Sublimed (sometimes colloquially referred to as the Elder civilizations due to the fact that they are no longer around), groups that have reached a high level of technical development and galactic influence but subsequently abandoned the physical Reality, ceasing to take serious interventionist interest in galactic civilization. They are also contrasted with what some Culture people loosely refer to as "barbarians", societies of intelligent beings which lack the technical capacity to know about or take a serious role in their interstellar neighbourhood.

The Involved are also contrasted with hegemonising swarms (a term used in several of Banks' Culture novels). These are entities that exist to convert as much of the universe as possible into more of themselves; most typically these are technological in nature, resembling more sophisticated forms of grey goo, but the term can be applied to cultures that are sufficiently single-minded in their devotion to mass conquest, control, and colonisation. Both the Culture and the author (in his Notes On the Culture) find this behavior quixotic and ridiculous. Most often, societies categorized as hegemonising swarms consist of species or groups newly-arrived in the galactic community with highly expansionary and exploitative goals. The usage of the term "hegemonising swarm" in this context is considered derisive in the Culture and among other Involved, and is used to indicate their low regard for those with these ambitions by comparing their behavior to that of mindless self-replicating technology. The Culture's central moral dilemma regarding intervention in other societies can be constructed as a conflict between the desire to help others and the desire to avoid becoming a hegemonising swarm themselves.