In the early 1980's, the IEEE 802.3 standard for Ethernet replaced the DIX standard. The IEEE or Institute of Electrical and Electronics Engineers defines industry-wide standards that promote the use and implementation of technology. Instead of keeping control of the Ethernet standard as a
proprietary standard, Xerox ceded control to the IEEE, which has committees that define standards for a variety of electronics. These committees are named for the standards they publish. The IEEE 802 committee sets the standards for networking. However, this committee is split into several smaller sub-committees such as IEEE 802.3 and IEEE 802.5.

Sub-Committees

801.1 Higher Layer LAN Protocols
802.2 Logical Link Control
802.3 CSMD/CD (aka Ethernet)
802.4 Token Bus - dormant
802.5 Token Ring
802.6 MAN (Metropolitan Area Network)
802.7 Broadband
802.8 Fiber Optics
802.9 Isochronous LAN
802.10 Security
802.11 Wireless
802.12 Demand Priority/100baseVG
802.13 Not Used
802.14 Cable Modems

Some say 802.3 & Ethernet, from the original Xerox standard, are not the same because they differ in minor details. Though this is actually true in a way, many of us use the term IEEE 802.3 & Ethernet interchangeably.