The OpenGL Shading Language (GLSL) is a high-level language used to create shaders that run on graphics processing units (GPUs). These shaders are responsible for rendering objects and scenes in 3D graphics applications. GLSL provides a flexible and powerful toolset for creating shaders that can handle a wide range of effects, from simple color changes to complex lighting and shadowing effects. GLSL programming requires knowledge of computer graphics, geometry, and mathematics, and is typically used by game developers, graphic designers, and other professionals in the field of computer graphics.