Commonly used PoE power supply equipment has outdoor PoE switch and PoE injector, although they can be for the other end of the network equipment power supply, but somewhat different.
PoE switches can work independently and transmit data and power signals simultaneously. It can be connected to a device that needs power supply.
PoE injector only the role of power supply, without the role of data transmission. So need to use with the switch, which is their essential difference.