DxDiag

DxDiag is a diagnostic utility distributed with the DirectX package of application programming interface (API) software and multimedia components. DxDiag stands for DirectX Diagnostics. It is a tool used to generate reported on components related to DirectX, such as drivers that handle audio and video hardware. You can run DxDiag on a system with DirectX installed by using the Run box and typing "DxDiag".

Other DirectX related glossary:

DirectDraw
Direct2D
Direct3D
DXGI
DirectInput
DirectPlay
DirectPlay Voice
DirectSound
DirectSound3D
DirectMusic
DirectX Audio
DirectX Media
DxDiag
DirectX Media Objects
DirectSetup
XAudio2