This module or an Ethernet Shield uses the W5100 which provides a set of TCP/IP protocols, MAC (Media Access) and PHY (Physical Interface) in one network chip, with support for the SPI bus interface.
The Ethernet Arduino IDE library that comes with the Arduino IDE is designed directly for W5100 and is supported on this product.
Your Arduino can be a Web Server with this brick!
a BOTTOM view of the module connector.
Source URL : http://arduino-info.wikispaces.com/Ethernet