What is Ethernet?

Types of Ethernet cables
The IEEE 802.3 working group approved the first Ethernet standard in 1983. Since then, the technology has continued to evolve and embrace new media, higher transmission speeds and changes in frame content.
Below are some of the changes:

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  802.3ac was introduced to accommodate VLAN and priority tagging.
  
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  802.3af defines Power over Ethernet (PoE), which is crucial to most Wi-Fi and Internet Protocol (IP) telephony deployments.
  
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  802.11a, 802.11b, 802.11g, 802.11n, 802.11ac and 802.11ax define the equivalent of Ethernet for WLANs.
  
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  802.3u ushered in 100BASE-T -- also known as Fast Ethernet -- with data transmission speeds of up to 100 Mbps. The term BASE-T indicates the use of twisted-pair cabling.
  

Gigabit Ethernet boasts speeds of 1,000 Mbps -- 1 gigabit or 1 billion bits per second (bps) -- 10 GbE, up to 10 Gbps, and so on. Over time, the typical speed of each connection tends to increase.
Network engineers use 100BASE-T to do the following:

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  connect end-user computers, printers and other devices;
  
• 
  manage servers and storage; and
  
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  achieve higher speeds for network backbone segments.
  

Ethernet cables connect network devices to the appropriate routers or modems. Different cables work with different standards and speeds. For example, Category 5 (Cat5) cables support traditional and 100BASE-T Ethernet. Category 5e (Cat5e) cables can handle GbE, while Category 6 (Cat6) works with 10 GbE.
Ethernet crossover cables, which connect two devices of the same type, also exist. These cables enable two computers to be connected without a switch or router between them.