A bee feeder is used as a container for the bees’ food if they are experiencing a shortage in their own supply. This is usually not a common occurrence but when it does, beekeepers need to intervene to ensure that the bees do not starve to death.
However, it is a common misconception that beekeepers should leave feeders throughout the hive, this is simply not required.
Bees are self-sufficient insects so what should be done is to only lend a helping hand, not to spoon-feed them.