A reserve is a highly advanced, highly stocked underground bunker, that can act as a home for an upwards of 1,000 people to last out an apocalypse. They're stocked based on projected population growth rate and number of insulation breaches that will spoil food, but most reserves will average lasting around 230 years before the inhabitants must emerge. There are 94 official reserves and 6 unofficial reserves in Scetane.
In truth, dozens of the reserves in place were not designed to save thousands of people to restart society, centuries later. Many of them were designed as social, chemical, and military experiments on the human body and the human mind. There is a reserve for testing the impact of white noise, a reserve for human ambition when food stores suddenly go empty, and a reserve for cloning the perfect super soldier. These official purposes, however, were never publicized.