1973 #Ethernet as one of the defining information technologies in modern communication was developed at #PARC by Chuck Thackers for #Alto#Computer s. What Bob Metcalf, Butler Lampson, and Dave Boggs built for the #ARPAnet is connecting us all today— via the #Internet, & @fediverse.
Ethernet is a protocol, not a medium. Cat5/5e/6/6a/7/etc are most commonly used as the physical link layer for Ethernet, but they’re just twisted pair copper.
Ethernet can also be run over coaxial, fiber, or the air.
You are conflating layer 1 technologies (shielded or unshielded twisted pair, CAT3 through CAT7) with layer 2 technologies (Ethernet).
Layer one is the physical media itself. Alternatively some modern-day L1s are MoCA, Powerline, WiFi, fiber, and of course, 1000BaseT, whose standard specifies CAT5e or higher STP.
Layer two is how those bits get sent in that media. Ethernet is, by and far, the most familiar L2.
And then layer three is where we get to networking and start talking about IP addresses (IP being the most familiar L3).