Final answer:
The primary function of Photoshop is image editing, where it provides a comprehensive suite of tools for enhancing and manipulating raster images according to graphic design principles.
Step-by-step explanation:
The primary function, or purpose, of Photoshop is image editing. Photoshop is a software that allows graphic designers to create, enhance, or otherwise modify images. They can manipulate various elements of an image such as light, which is used to highlight or obscure parts of the image, and line, which guides the viewer's eye across the composition. Graphic designers utilize principles such as balance, unity, and variety to arrange elements in a layout. Moreover, Photoshop aids in employing basic photo composition techniques like the rule of thirds, steady camera, level horizon, fill the frame, and removing distracting backgrounds to improve the overall look of an image.
Photoshop is not primarily designed for multiple-page layout (which is often the domain of software like Adobe InDesign), vector graphic creation (more suited to Adobe Illustrator), or line art illustration (although it can manage some aspects of these tasks). Its robust toolset is ideal for editing and composing raster images, retouching, and adding effects to create high-quality visuals.