Introduced with Windows 95, Direct3D's feature set allows for a dependable set of functions that graphics engine programmers can call upon for any supporting graphics card, ending developer decisions over which individual graphics accelerators API they should code for.
Newer Direct3D versions have increased feature sets allowing increased visual fidelity by supporting the features of newer advanced GPUs. Direct3D's importance is so well-recognized for game and general real-time rasterized 3D performance that Microsoft has foregone updating older OS versions’ Direct3D. Instead, the company offers it as a feature exclusive to a newer version of Windows as it did with Vista and Direct3D 10.
Microsoft develops Direct3D with input from GPU makers and programmers. Direct3D’s competitor is OpenGL. While performance was often OpenGL's strong point, Direct3D maintained dominance in Windows due to Microsoft's ability to bring some key features to market first.