GNU Image Manipulation Program (GIMP) is a popular open-source photo editor that offers many features comparable to Photoshop. It supports layers, masks, and a wide range of image editing tools. While it may not have all the advanced features of Photoshop and its interface might not be as modern, GIMP provides a free alternative for individuals who want to edit photos without spending money on software. It is available for Windows, macOS, and Linux.