Ethernet is a way of connecting computers together in a local area network or LAN. It has been the most widely used method of linking computers together in LANs since the 1990s. The basic idea of its design is that multiple computers have access to it and can send data at any time. This is comparatively easy to engineer.
If two computers send data at the same time, a collision will occur. When this happens, the data sent is not usable. In general, both computers will stop sending, and wait a random amount of time, before they try again. A special protocol was developed to deal with such problems. It is called Carrier sense multiple access with collision detection or CSMA/CD. There are different Ethernet standards. Today, Ethernet cables look like thick telephone cables. They connect to boxes called hubs or switches. Each cable runs from a computer's network interface card (NIC) to such a box. This cable is called 10BaseT or 100BaseT, or 1000BaseT Cable.

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