A hub is a repeater. Anything sent on one port automatically goes out to all other connected ports. The difference between a hub and a repeater is that a repeater, repeats the signal out of a single interface. A hub repeats the signal to multiple interfaces simultaneously. Consequently a hub is known as a “multi-port repeater.”
Communications within a hub is half duplex. This means that 2 devices on the hub can’t communicate at the same time. If you have 1 device sending traffic, all other devices must wait until that 1st device finishes, in order to send their traffic.
A hub shares bandwidth with all ports. Hubs become less efficient as the number of connected devices increases. Hub networks are slower than switched networks. Ethernet hubs operate at 10 megabit / 100 megabit per second. No Gigabit speed hubs. Hubs may be difficult to find today because the technology doesn’t scale as you put more traffic on the network.
