A flow limiter or flow restrictor is a device to restrict the flow of a fluid, in general a gas or a liquid.
Some designs use single stage or multi stage orifice plates to handle high and low flow rates.
As a safety valve to provide limited flow after closing in the event of a broken hose.
Reduce pressure in a system
Reduce flow of fluid (velocity) through a system. e.g. to reduce water usage in a shower.