HLSL (High-Level Shading Language) is Microsoft's programming language for writing shaders for DirectX. Shaders run on the GPU to compute vertex colors, positions, and pixel attributes. HLSL syntax is similar to GLSL but optimized for the DirectX pipeline and Windows/Xbox platforms. Pixel shaders (fragment shaders) compute colors, vertex shaders compute positions, and compute shaders perform parallel computation. HLSL is the industry standard for game studios using Unreal Engine, custom DirectX engines, and Windows-based graphics applications.