Planet Chili

Title says all.

Whats the difference and which is used more commonly in games/what games are programmed in each language/which is better/etc.

-Mtdewd

You could write book on that topic I'm sure, but I'm not inclined to do so

One advantage that DirectX has over OpenGL is that it tends to expose more of the functionality of the hardware and tends to get new versions quicker.

One advantage of OpenGL is that it doesn't tie you down to the Windows platform.

These days, as far as I know, most games support DirectX exclusively, while some support both. CAD applications tend to require or prefer OpenGL though.

doesnt OpenGL mean open source and its free to use unlike Direct X which is a Microsoft API and you have to pay royalties if you were to create a game with it?

You're partially correct. OpenGL is more of an open standard than DirectX. However, there are no royalties required for PC games which use the DirectX API (Xbox is a different story).