newbie: global coords Vs. local coords, how to ?

Hi All,

I am using OpenInventor as part of my graduate program thesis. I'm 
developing a 3D application and need to have local system in global
system.
Can anyone explain the difference between global coordinates and local 
coordinates and how do I develop such a system using OpenInventor / Coin3D
?

Any help is greatly appreciated.

Joshua Robinson
University of Florida
Computer Engineering Student