EZ Mask is an easy to use interactive image masking tool capable of
extracting almost any object in an image--even if you are dealing with fine
hair detail, smoke, or reflections. This extraction process creates what is
known as a mask--essentially a black and white cutout. White mask areas are
extracted, black areas not, and gray areas in between represent a level of
transparency. Once a mask is extracted, the foreground object can be
seamlessly composed onto a new background in Adobe Photoshop or Photoshop
Elements as well as apply filter and image corrections only within the area
defined by the mask.

To work this magic, EZ Mask iteratively estimates the transparency value for
every pixel in the image, based on a small sample of foreground (what you
want to cut out) and background pixels marked by simple strokes on the image.