OpenGL stands for Open Graphics Library, and is a 3D graphics API, used to interpret calls made from games and other software into on-screen results.
Its competitor, DirectX, is only available on Microsoft platforms, and on Linux through WINE as a limited implementation. OpenGL is dominant on Mac OS X and Linux and is also available for Microsoft Windows.
SGI licenses OpenGL code which AMD and NVIDIA may use in their drivers. The open source implementation, Mesa 3D, is an unaccelerated software implementation provided with XFree86 and XOrg for Linux.
- OpenGL at Wikipedia