An Ethernet hub is a form of repeater with multiple network ports or connections. Traffic entering any of the ports is repeated to every port on the hub. The typical purpose of a network hub is to extend a network circuit to multiple endpoints.
Network hubs are simple hardware devices as compared to network bridges and switches. The main weakness of a hub is all traffic is repeated where network bridges and switches intelligently forward traffic. Ethernet networks can become saturated with network traffic and broadcasts and network hubs do not filter Ethernet packets but forwards all traffic.