Replicators convert energy into matter, producing food, tools, clothing and spare parts on demand aboard starships, stations and homes.
Replicators use technology closely related to transporters, rearranging matter into a stored pattern. Users simply name an item and the device creates it within seconds. On the original Enterprise, food synthesizers performed a similar role, while 24th-century replicators could produce almost any non-living object within their library.
Replicators reshaped Federation society by removing material scarcity. They still have limits. They cannot create living things, cannot easily reproduce certain complex materials, and use significant power, which forced Voyager's crew to ration replicator use far from home and gave Neelix a role running the ship's galley.