What is PoE in Networking?

IEEE 802.3at-2009 standard is commonly known as “PoE+” or “PoE Plus”, and it is the later update to the IEEE 802.3af-2003 “PoE” standard. It defines PoE Classes 0-4, where Classes 0-3 are incorporated from the older 802.3af “PoE” standard under “Type 1”, and “Type 2” only includes Class 4 with maximum power at PD being 25.5W.