Definition - What does IEEE 802.3 mean?
IEEE 802.3 is a set of standards put forth by the Institute of Electrical and Electronics Engineers (IEEE) that define Ethernet-based networks as well as the name of the working group assigned to develop these standards.
IEEE 802.3 is otherwise known as the Ethernet standard and defines the physical layer and the media access control (MAC) of the data link layer for wired Ethernet networks, generally as a local area network (LAN) technology.
Techopedia explains IEEE 802.3
IEEE 802.3 specifies the physical and networking characteristics of an Ethernet network, like how physical connections between nodes (routers/switches/hubs) are made through various wired media like copper coaxial or fiber cable.
The technology was developed to work with the IEEE 802.1 standard for network architecture and its first released standard was Ethernet II in 1982, which featured 10 Mbit/s over thick coax cable and featured frames with a "Type" field. In 1983 the first standard with the name IEEE 802.3 for 10BASE5 (thick Ethernet or thicknet) was developed. It had the same speed as the previous Ethernet II standard, but the "Type" field was replaced by a "Length" field. 802.3a followed in 1985 and was designated as 10BASE2, which was essentially the same as 10BASE5 but ran on thinner coax cables, therefore it was also known as thinnet or cheapnet.
There are a multitude of additions and revisions to the 802.3 standard and each is designated with letters concatenated after the number "3". Other notable standards are 802.3i for 10Base-T for using twister pair wire and 802.3j 10BASE-F for using fiber-optic cables.