What Is Photoshop

Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated.
Adobe's 2003 "Creative Suite" rebranding led to Adobe Photoshop 8's renaming to Adobe Photoshop CS. Thus, Adobe Photoshop CS5 is the 12th major release of Adobe Photoshop. The CS rebranding also resulted in Adobe offering numerous software packages containing multiple Adobe programs for a reduced price. Adobe Photoshop is released in two editions: Adobe Photoshop, and Adobe Photoshop Extended, with the Extended having extra 3D image creation, motion graphics editing, and advanced image analysis features.^[3] Adobe Photoshop Extended is included in all of Adobe's Creative Suite offerings except Design Standard, which includes the Adobe Photoshop edition.
Alongside Adobe Photoshop and Adobe Photoshop Extended, Adobe also publishes Adobe Photoshop Elements and Adobe Photoshop Lightroom, collectively called "The Adobe Photoshop Family" by Adobe. In 2008, Adobe released Adobe Photoshop Express, a free web-based image editing tool to edit photos directly on blogs and social networking sites.
Adobe support only Windows and Mac versions of this program but with Wine, CS4 version of Photoshop can work on Linux.

Photoshop CS5
Create powerful images with the professional standard

Source:http://en.wikipedia.org/wiki/Adobe_Photoshop