One of the biggest advantages of IP cameras is the ability to transmit signal and power to the camera over a single cable. This feature is called PoE - Power over Ethernet. This feature allows you to significantly save on cable and simplify installation.
In order to transmit power over an Ethernet cable (usually a Category 5 UTP cable), a special device is needed - a PoE injector that injects power into the signal cable.
The PoE injector has an input, an output and a 220v power cable with a plug at the end. A cable from your switch or computer is connected to the input (LAN), depending on where the signal comes from, the IP camera itself is connected to the output (PoE), which is powered by the injector.
As a rule, modern IP cameras use PoE standards IEEE 802.3af, IEEE 802.3at, according to which 48V voltage is transmitted through the cable. The increased voltage (low current) allows sufficient power to be transmitted through the thin strands of the UTP cable to power the IP video camera itself.