The difference is of added features like

Smart Filters Nondestructive Smart Filters allow you to visualize changes without altering original pixel data.
Advanced compositing Create more accurate composites by automatically aligning multiplephotoshop layers or images based on similar content.
Better raw image processing Process raw images with increased speed and superior conversion quality using the Adobe Photoshop Camera Raw plug-in, which now adds support for JPEG and TIFF formats; new tools including Fill Light and Dust Busting; compatibility with Adobe Photoshop LightroomT software; and support for over 150 camera models.