Is this Direct3D improves graphics in games? If we do not have it, can we still play any game?
Direct3D is an API from Microsoft which is found in the DirectX libraries. Yes, it is used in games and applications and it's a 3D renderer for objects. It's used along OpenGL to provide stunning results in terms of graphical programming. Direct3D is implemented by default into your OS starting Windows 95 in form of DirectX libraries.