POE is the abbreviation for Power over Ethernet and describes the power supply of the connected device via the existing network cable.
By using POE, one saves the external power supply and accordingly the cable laying.
The device is then connected to a switch with only one cable to both transmit the data and supply the device with power. A simple way to install surveillance cameras!
It is necessary, that
a. the connected device is POE-capable
b. a so-called POE switch is used.
POE switches are a standard product nowadays and hardly differ in price. Please make sure that the switch is actually a POE switch.