Starships are both interstellar vehicles and living spaces. In the Culture, Ships were also ambassadors of the Culture itself. Each Ship was sentient; that is, it embodied a Mind. The physical Ship was to the Mind what the human body is to the brain.[1]
While the majority of Culture citizens lived on Orbitals, many also lived permanently aboard Ships.[1] The very largest of Culture Ships, the General Systems Vehicles (GSVs), were microcosms of the Culture itself. All the knowledge, technology, and production capability of the Culture as a whole is also embodied within a GSV, the whole contained within each part.