A hub is a really old piece of network technology. It’s a physical device with ports on the front, enabling other devices to connect with cables.
If there aren’t enough ports on the hub, several hubs can be chained together to add more ports.
Hubs are now old and out of date. They have been replaced with switches. However, due to their physical similarities, some people call switches ‘hubs’.
Switches replaced hubs as switches have some intelligence built in, while hubs do not. Switches also perform much better than hubs.
It is becoming very rare to see hubs in use these days.