Arduino Shields?

I am going to buy an Arduino and CNC shield kit when I purchase my CNC machine.

http://www.ebay.com/itm/CNC-V3-Shie...hash=item4ae9f5cf60:m:meEBpMpDQMrHN8xWdGJWAbA

I would also like to add an Ethernet shield.

I see there are Ehternet shields....

Arduino Shields?