this is about hardware. what is the different about this 3 hardware= router, switch and hub?

Hubs and switches are used to network multiple computers together.

A hub is dumb... Any traffic that comes in is broadcast to all the ports. All computers on a hub can hear what's going on between the other computers, they just don't normally pay attention to anything that isn't meant for them.

A switch is smart... It knows which computers are on which port, and sends info out to only the one port.

A router sits between a computer or network on the inside, and a network on the outside. The most common use is to between a home network and a broadband connection to the internet. It routes traffic from one side to the other. It might incorporate a hub or switch, so you can use it as such. It might also incorporate a firewall to protect the computer or network on the inside.

thanks ranger_nemo, i think that is enough for beginner like me. maybe i will get better understanding when it comes to practice.