Power over Ethernet (PoE) is a technology that allows delivery of power over Category 3 or better Ethernet cabling, along with Ethernet data. Compared with traditional systems that have separate power supply lines, PoE reduces the cost of installation and maintenance of devices in remote location control (such as WLAN access point and IP cameras), and no need to re-wire the AC infrastructure to provide centralized power backup for devices. PoE just connects devices into a single network cable.
IEEE 802.3 PoE defines standards for signaling between the powered device (PD) and the power sourcing equipment (PSE).
Power Device: The consumer of Power over Ethernet
Power Sourcing Equipment: The device sends power over Ethernet. It includes
Endspan PSE integrates PoE into Ethernet switches .
Midspan devices are just for organizations looking to upgrade a network without replacing existing switches. These devices receive data lines from the switch and insert power over the spare pairs, providing data and power out to the PD.