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The Khronos Group, the consortium of hardware and software companies that governs OpenGL, OpenCL, and other related specifications, made no bones about its intentions for OpenGL 4: providing standardized support for Direct3D 11 features to OpenGL developers was the prime concern. Direct3D 11 integrated two key features into the graphics pipeline: hardware tessellation and compute shaders. The former allows the video card to synthesize polygons programmatically, enabling considerably smoother, more natural looking curved surfaces. The latter is a key part in the development of using the GPU for general-purpose computation (GPGPU)—not just for producing graphics, but for performing various kinds of high-performance math.
Link: http://arstechnica.com/software/news/2010/03/opengl-4-spec-arrives-with-direct3d-11-feature-parity.ars
Also: http://www.geeks3d.com/20100315/overview-of-the-new-features-of-opengl-4-0/