Can someone explain to me the function of ethernet switch and what is its difference with router? Thank you.

A router makes you look like an ISP. A router is required to PROPERLY hook up many machines to the internet. ICS, HUB, and USB are very STUPID connections to the internet. They are a hacker's and virus's dream connection. They have alot of connection problems too. A router allows multiple computers to connect to the internet as one. Hard to hack into. A router by nature has one LAN port. Most are sold with a 4 port switch attached internally to that one LAN port so as to get 4 lan ports. A hub and switch are like splitters. A hub will send data to all computers while the switch will send data to the computer that needs it. You need 4 or more machines to get any advantage out of a switch.

A router makes intelligent packet forwarding decisions based on TCP/IP addresses. It is used so computers can communicate between different network subnets. A hub provides network connectivity to multiple computers. It is very stupid, and broadcasts packets out of all nodes. It's just a cheap and easy way to connect a few computers. Network collisions abound. A switch is like an enhanced hub. It doesn't broadcast out of all nodes. It looks at MAC addresses and makes sure that the right computer gets the packet. This prevents network collisions.