GLSL, or the Graphics Library Shader Language, is a high-level shading language with a syntax based on the C programming language. It was created by the Khronos Group, with the intention of giving developers more control over the graphics processing pipeline.
GLSL is used to write shaders, which are programs that run on the GPU. Shaders are used to calculate the color of each pixel on the screen, as well as other effects like lighting and shadows.
GLSL is a powerful tool for graphics programmers. It allows developers to write shaders that are more efficient and easier to read than low-level languages like HLSL and Assembly.
GLSL is also portable, meaning that shaders written in GLSL can be run on any platform that supports OpenGL. This makes it a popular choice for cross-platform development.
If you're interested in learning GLSL, there are a few resources to get you started. The Khronos Group provides an online reference for the language, as well as a specification. The book "OpenGL Shading Language" by Randi J. Rost is a good introduction to writing shaders.