This article is from the Ethernet FAQ, by James Messer James@NetworkUptime.com with numerous contributions by others.
Ethernet is the IEEE 802.3 series standard, based on the
CSMA/CD access method that provides two or more stations to share a
common cabling system. This access method, Carrier Sense Multiple
Access with Collision Detection, is the basis for Ethernet systems
which range from speeds of 1 Mb/s through 1000 Mb/s.
The design goals for Ethernet were to create a simply defined
topology that made efficient use of shared resources, was easy to
reconfigure and maintain, provided compatibility across many
manufacturers and systems, while keeping the cost low.