PoE switch/injector → Ethernet cable → PoE splitter → device
The splitter takes the combined data + electrical power coming through the Ethernet cable and outputs:
Power — usually through a DC connector
Network data — through an Ethernet/RJ45 connection
Example
If you have a device such as a Wi-Fi access point, IP camera, or small network device that doesn't support PoE but needs both internet and power, a PoE splitter can allow you to use a single Ethernet cable to reach it.