Ethernet is the local area network most used nowadays.
Usual Arduino boards don't provide Ethernet ability. There is one board named Arduino Ethernet that provides native Ethernet and network features. By the way, it doesn't provide any USB-native features.
You can find the reference page here: http://arduino.cc/en/Main/ArduinoBoardEthernet.
Arduino Ethernet board with the Ethernet connector
We are going to use the Arduino Ethernet Shield and a 100BASE-T cable with the Arduino UNO R3. It keeps the USB features and adds Ethernet network connectivity and provides a nice way to link our computer to the Arduino with a much longer cable that USB ones.
The Arduino Ethernet Shield
If you look for the Arduino Ethernet module, you must know they are sold either with or without the PoE module.
PoE stands for Power over Ethernet and is a way to supply power to devices through Ethernet connections. This requires two parts:
A module on the device that has to be supplied
A network...
