newbie question: what is openGL

hello everyone!

I’ve wanted to create a 3d game but I had no idea how to make one until I discovered lwjgl.
Only one problem , they are talking a lot about openGL and I didn’t knew what that was so I googeld it.
Now I kinda know what it is , but I don’t know how to use it … when I see some OpenGL code I’ve no clue what it does and stuff like that …

So basicly the question is: how can I use openGL , are there any tutorials I can follow ? or a good book ?

Sorry for my terrible english

thanks!