A PSD file is an image file created by Adobe Photoshop, a professional image-editing program. It may include image layers, adjustment layers, layer masks, annotation notes, file information, keywords, and other Photoshop-specific elements.
Photoshop documents support RGB, CMYK, grayscale, monochrome, duotone, indexed color, Lab color, and multichannel color modes. The color mode can be changed within the submenu.
While PSD files are saved in a proprietary format, they can be opened directly with Apple Preview, which is included with Mac OS X. They can be also opened by the media programs included with Windows 7 if the correct codec, such as the Ardfry PSD codec, is installed. These programs include Windows 7 Photo Viewer, Windows 7 Media Center, and Windows Media Player.
NOTE: Autodesk Pixlr can open simple PSD files but is not able to open more complex and larger PSD files.