Direct3D is an API (application programming interface) created by Microsoft that is used to render three-dimensional objects. Introduced with the DirectX API, it allows these objects to be rendered without sacrificing performance. Additionally, it allows software applications, including games, to be run in full-screen mode. If a video card is available, Direct3D can utilize hardware acceleration. Although it is owned by Microsoft, it can work with other platforms by using Wine, an open source program.
Programming for DirectX is done using an SDK (software development kit), which is available for free download.
Microsoft released the first version of Direct3D in 1995, as a part of DirectX 2.0. Windows 95 OSR2 was the first operating system to include Direct3D technology. Since then it's continued to be used and is also used in each generation of their Xbox gaming consoles. Since version 8, it also renders two-dimensional graphics, which is a task previously handled by DirectDraw.