It is for your left hand since most gamers use the WASD keys for movement. Here's a video of a similar design being used to play Quake. https://www.youtube.com/watch?v=xyVSANPnLlg
[EDIT] The Azeron comes in both right- and left-handed versions so that's why some images show a right hand. The Azeron works similarly to one half of a DataHand keyboard.
This old infomercial shows how they're used https://www.youtube.com/watch?v=T7UajuYCIyk