What is the difference between a hub, switch, and router?

A hub forwards packets it receives through one port to every other port on the device.

A switch will read packet headers and identify which machines are connected to which port based on the information they send. Any packets addressed to those machines will only get sent to that port of the switch.

A router looks at packet headers to determine which port it needs to forward a packet through, and also will translate packets between different protocols if needed. A router can also define subnets and will filter traffic as needed. Routers usually include DHCP, port forwarding capabilities and a whole host of other things usually controlled by software and therefore user customizable.