Arduin Yun/ Yun Shield

The question I have is about the Arduino Yun and if the Yun Rev2 is the same as a Yun Shield?

I was looking at a project in the project center on the site and they are using a Arduino Yun Shield to give wifi to a Due board and didn’t see a Yun shield on the products page hence the question.
https://www.arduino.cc/en/Tutorial/LibraryExamples/RemoteDueBlink