PoE technology relies on the IEEE 802.3af and 802.3at standards, which are set by the Institute of Electrical and Electronics Engineers and govern how networking equipment should operate in order to promote interoperability between devices.
PoE-capable devices can be power sourcing equipment (PSE), powered devices (PDs), or sometimes both. The device that transmits power is a PSE, while the device that is powered is a PD. Most PSEs are either network switches or PoE injectors intended for use with non-PoE switches.
Common examples of PDs include VoIP phones, wireless access points, and IP cameras.