Irrlicht Engine

I'm new to Graphics programming so my questions are:

1. What is the difference between Dx and OpenGl.

2. Irrlicht can use both ?

3. Can Iuse OpenGl function classes in Irrlicht or I must follow the rules that are set by devs?

Anything else that explains to me the world of graphics would be useful

Thanks

1. DirectX is Microsoft's graphics library and Windows-only, OpenGL is cross-platform.

2. Yes.

3. You can extend the Irrlicht engine easily. OpenGL functions are used in the background.

there are many differences between Dx and OpenGL. For developing with irrlicht, however, the differences really only matter much when you get to modding the engine. Some things are implemented somewhat better in Dx than OpenGL, but IrrlichtNX, the rest of the community, and the latest release have I think left few differences between irrlichts capability with the two rendering api's