OpenGL 4.0 is a graphics rendering API that allows developers to create 2D and 3D graphics for applications like video games and simulations. Released in 2010, it introduced new features such as improved shaders, enhanced texture handling, and better support for modern graphics hardware, enabling more realistic visuals and complex scenes. This version of OpenGL also includes support for OpenGL Shading Language (GLSL) 4.0, which allows programmers to write custom shaders for more control over rendering. Additionally, it provides features like geometry shaders and tessellation, which help in creating detailed and dynamic graphics efficiently.