OpenGL, stands for “Open Graphics Library,” is mainly considered as API (Application Programming Interface) designed for rendering 2D and 3d graphics. The API is typically used to interact with a graphics processing unit (GPU), for to achieved hardware rendering. 

All the operating systems and hardware device supports OpenGL. By using OpenGL developers can use same code for rendering and developing some graphics images, like 2D and 3D graphics, and render graphics on Mac, PC, or mobile device. OpenGL standard is already implemented inside of your OS GPU driver.

There are many version of the OpenGL specification. OpenGL version are not same like most Direct3D version, which is usually change most of the API. If you wrote code for one of the version of OpenGL will almost always work on later version of OpenGL. OpenGL is easy choice of graphics development.

Example, OpenGL includes drawing objects like polygons, colors shades, textures of polygon, transforming polygons and rotating object. OpenGL is commonly used for video games also, and for managing lighting effects, such as light source, shading and shadows. And it also used for graphics library for many CAD application, such as Blender and AutoCad, manipulate graphics and images.