Definition:

IEEE 802.3 is a working group and a collection of IEEE standards produced by the working group defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. This is generally a local area network technology with some wide area network applications. Physical connections are made between nodes and/or infrastructure devices (hubs, switches, routers) by various types of copper or fiber cable. 802.3 is a technology that supports the IEEE 802.1 network architecture. 

What 802.3 Standard Originally Defined Poe Functionality When Was the Standard Enhanced 

Powering network devices can sometime present problems, especially if they are located remotely. One convenient solution is to supply the power over an Ethernet LAN cable. Power over Ethernet, is defined under two IEE standards, namely IEEE 802.3af and later IEE 802.3at which defined a number of enhancements.

This Power over Ethernet, PoE is now being used for a wide variety of applications including powering IP telephones, wireless LAN access points, webcams, Ethernet hubs and switches and many more devices. It is convenient to use and as a result, Power over Ethernet is widely used and many products are available. The main  advantage of Power over Ethernet  is that you can save the power supply cable and install  devices  with  Ethernet  interface  in  places  of  di fficult  access  or  in  ar eas  in  which  a  lot  of   cables would be an interference .

Ethernet, 802.3 is defined under a number of IEEE standards, each reflecting a different flavour of Ethernet. One of the successes of Ethernet has been the way in which it has been updated so that it can keep pace with improving technology and the growing needs of the users. As a result of this the IEEE standards committee for Ethernet has introduced new standards to define higher performance variants. Each of the Ethernet IEEE 802.3 standards is given a different reference so that it can be uniquely identified. in addition to this the different IEEE 802.3 standards may be known by other references that reflect the different levels of performance.

Conclusion:

802.3 is a standard specification for Ethernet, a method of physical communication in a local area network (LAN), which is maintained by the Institute of Electrical and Electronics Engineers (IEEE). In general, 802.3 specify the physical media and the working characteristics of Ethernet. The original Ethernet supports a data rate of 10 megabits per second (Mbps) and specifies these possible physical media.