What more can be said about Photoshop? The word photoshop has been adopted as the generic name for all photo processing programs.
Photoshop indeed is the gold standard for processing digital photos, although it has so much in it that many people find it too complex. We use Photoshop for one tool that they implement better than any other program: automatically separating multiple photos from a single scan of an album page. For most other processing tasks we use either Lightroom, Picasa or Paintshop Pro -- largely because we have learned those programs inside-out. We have never taken the time to learn all of the details of Photoshop.
You can find more information about Photoshop at: