Microsoft has shared the date and time of the reveal of DirectX 12. Apparently, they will have AMD, Nvidia, Intel, and Qualcomm there with them.
DirectX is an API, or application programming interface standard, used for multimedia on Windows platforms. The standard has been most used for gaming and movies, and has been integral for PC gaming for much of its history.
However, DirectX has faced stiff competition from other, more open APIs, as Windows itself has faced challenges from other platforms, including iOS, Linux (including Android), and even Facebook. Even AMD itself is busy developing its own low-level API, Mantle.
We have little info on what DirectX 12 will have, but Windows is still a major gaming platform. There can be no doubt that the upcoming reveal this March 20 will be one, if not the, highlight of GDC.