OpenGL...

OpenGL provides the programmer with an interface to graphics hardware. It is a powerful, low-level rendering library, available on all major platforms, with wide hardware support. It is designed for use in any graphics application, from games to modeling to CAD. Many games, such as id Software’s Doom 3, use OpenGL for their core graphics-rendering engine.

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OpenGL stands for “Open Graphics Library.” “Open” is used because OpenGL is an open standard, meaning that many companies are able to contribute to the development. It does not mean that OpenGL is open source.

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OpenGL was originally developed by Silicon Graphics, Inc. (SGI) as a multi-purpose, platform-independent graphics API. Since 1992, the development of OpenGL has been overseen by the OpenGL Architecture Review Board (ARB), which is made up of major graphics vendors and other industry leaders, currently consisting of 3DLabs, ATI, Dell, Evans & Sutherland, Hewlett-Packard, IBM, Intel, Matrox, NVIDIA, SGI, Sun Microsystems, and Silicon Graphics. The role of the ARB is to establish and maintain the OpenGL specification, which dictates which features must be included when one is developing an OpenGL distribution.

source: Begining OpenGL Game Programming