Photoshop is a computer program by Adobe that is used for altering photographs prior to printing. Basic changes that may be made are color correction, brightness, contrast, and removal of scratches or dust spots. Photoshop has a range of tools for altering or adding content. Tools such as the healing brush will copy one area of the image to another area. This allows for example the removal of a cow from a field.
Photoshop is available in several versions for professional use, and there is a version, Photoshop Elements, for home use.