Range mask is a method to fine tune the mask of a local adjustment. That means you first have to apply a local adjustment before you can activate it.
Hi, vinsolo! Here's a quick how to: Pick the radial filter tool and make an adjustment anywhere on your image. Make sure you keep that adjustment selected and scroll down to where you see your Range Mask options. Click the dropdown next to the word "Off" and you should be able to select either Color or Luminance range mask. Depth mask is only available for images that have depth map data embedded. Hope that helps! Good luck!
Here you'll find some tutorials:
The Depth mask feture is only available for images that have depth map data embedded. As far as I know, at the moment only the iPhone is able to deliver such information.