An Ethernet hub is – well, Wikipedia does an impeccable job of summarizing what it is:
An Ethernet hub, active hub, network hub, repeater hub, multiport repeater, or simply hub is a network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the physical layer (layer 1) of the OSI model.
To which may be added, that hubs come into the picture with the movement from the pure bus topology of the original Ethernet, to the star topology used in later years, so they postdate Ethernet itself.
And I'm wondering to what extent did the falling price of the electronics that would go into a hub, influence the timing of the switch from bus to star topology.
What was the first Ethernet hub?