Open Graphics Library is a platform independent API specification for rendering 2D/3D graphics.It is generally implemented in GPUs

The openGL is a set of freely available specifications that basically define interfaces to be used by computer graphics programmers and the expected behavior. It is being used by application softwares (e.g. photoshop) and games since the 90's.

In the domain of IT security we are most likely to deal with webGL an openGL implementation for modern web browsers supporting HTML5. This allows the browser to access the capabilities of GPU to display graphics in the browser which can be considered as a security issue