GNU Image Manipulation Program, commonly known by its acronym GIMP, is a free and open-source raster graphics editor used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is extensible by means of plugins, and scriptable. It is not designed to be used for drawing, though some artists and creators have used it in this way.
GIMP version 2.10
Image editing encompasses the processes of altering images, whether they are digital photographs, traditional photo-chemical photographs, or illustrations. Traditional analog image editing is known as photo retouching, using tools such as an airbrush to modify photographs or editing illustrations with any traditional art medium. Graphic software programs, which can be broadly grouped into vector graphics editors, raster graphics editors, and 3D modelers, are the primary tools with which a user may manipulate, enhance, and transform images. Many image editing programs are also used to render or create computer art from scratch. The term "image editing" usually refers only to the editing of 2D images, not 3D ones.
A colorized version of originally black and white photo, colorized using GIMP
Original black and white photo: Migrant Mother, showing Florence Owens Thompson, taken by Dorothea Lange in 1936.
This is a photo that has been edited as a Bokeh effect, using a Gaussian blur.
Leonardo da Vinci's Vitruvian Man overlaid with Goethe's Color Wheel using a screen layer in Adobe Photoshop. Screen layers can be helpful in graphic design and in creating multiple exposures in photography.